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Patent Families: A Guide to Child Patent Applications



 

If you’ve filed a patent and want to protect a newer version of the invention, a child patent may be the tool for you. This child patent can use the original filing date of your first patent, which is a huge advantage.

 

A patent is designed to protect an invention and obvious modifications thereof. Filing a single patent to protect an idea is often sufficient. However, a patent owner can file a child application when they want to protect a new version of the invention or to address a competing product that falls within the scope of the parent application. Let's explore patent families and why a child patent might be right for you.

 

Basic overview

In the United States Patent and Trademark (USPTO), a child patent application is a patent application that is filed while the parent application is still pending. Here, “pending” means the child application must be filed before the parent is abandoned or issued. Another requirement is that the child patent must refer explicitly to the patent application. [1]. If you meet these two criteria, you can apply for a child application.

 

The above criteria must be assessed considering the cost of pursuing a child patent. Each child patent must be filed, prosecuted, issued, and maintained. There are legal costs and government fees associated with each of those actions. For example, the USPTO requires patent owners to pay fees to maintain the patent rights at 3.5 years, 7.5 years, and 11.5 years after the patent is issued. [2]. These fees need to be paid for each granted child application. Further, the cost is multiplied by the number of countries where the patents must be maintained. Navigating patent costs requires balancing immediate expenses with long-term strategic goals. The USPTO’s 2025 fee increases—particularly for continuations—heighten the need for proactive portfolio planning. 

 

The costs of filing child applications must be weighed against their substantial benefits. The primary benefit of a child application is that content shared between the child and parent applications receives the same filing date as the patent application. [1]. This enables the child application to avoid prior art filed after the parent application. In some cases, the USPTO cannot use the parent application as prior art to prevent issuing the child application. [3]. Patent applications that are joined in this way are called patent families.

 


Patent family best practices

 

Patent family members: Child patent types

A patent family is a chain of related patents and patent applications that claim priority to a shared parent application. The child application can be designated as the parent application for a later-filed application. This application linking may lead to an extended patent family where child applications have their own children and continue the chain. There are three types of child application: divisionals, continuations, and continuations in part (CIP).

 

Divisional application

A divisional application is filed when the patent examiner believes the claims in a patent application are directed toward two or more distinct inventions. When this happens, the examiner issues an office action containing a restriction requirement. The restriction requests that the applicant choose the claims covered by the patent. [4]. The applicant can file divisional applications to protect inventions not covered by the selected claims. For example, suppose the examiner believes the claims in a patent application are directed to three distinct inventions and issues a restriction. The applicant may file two divisional applications to cover the unelected inventions in that case. Divisional applications require no modifications to the claims or disclosure. These applications are tied to the specific claims identified in the restriction requirement.

 

Continuation application

A continuation application is filed when the applicant wants to modify the claims or specifications in some way that does not add new matter to the parent application. [5]. This flexible tool enables patent owners to build out a patent portfolio by strategically disclosing, but not claiming, multiple embodiments within the patent’s specification. A continuation application may be filed if the specification discloses a broader version of the invention than was captured in the allowed claims. Alternatively, a continuation application may be filed if the specification discloses a narrower version of the invention than was captured in the allowed claims.

 

The most essential requirement for a continuation application is that no new matter is added.  Successful continuations are granted the same filing date as the parent application. With strategic planning, a child application filed well into the 20-year term of the parent application can claim the same priority date.

 

CIP application

A CIP application is filed when the applicant wants to add new matter to the parent application. [6]. For example, a CIP is useful if the inventor wants to cover a new feature but does not want the parent application to be used as prior art. An important distinction between the continuation application and the CIP is the scope of the priority date protection. The new matter in the CIP is only protected from the CIP’s filing date. The CIP offers the applicant more freedom to modify the application than the continuation application. However, this freedom is tempered by limited priority date scope.

 

Timing for child applications

Child applications must be filed while their parent is still pending. However, it may be beneficial to file a child application as soon as prosecution starts or slightly before paying the issue fee. Determining when to tile a child application requires strategic planning that the patent professionals at Bright-Line IP can help you navigate.

 

In many cases, a child patent expires on the same day as the parent application. The patent examiner often requires the applicant to file a terminal disclaimer in exchange for the benefits gained by a child patent. The terminal disclaimer is a document that states that the term of the child patent will not extend beyond the 20-year exclusive right granted to the parent patent. [7]. In this way, the USPTO prevents inventors from gaming the system and indefinitely extending the life of a patent.

 

In a landmark case, Immersion Corporation v. HTC Corporation, the District of Delaware held that three patents filed on the same day as the issuance of their parent application were not filed during the pendency of the parent application and were, therefore, invalid. The court noted that patents automatically issue at 12:01 a.m. on their issue date, making same-day filings potentially too late. [8].

 

Patent family planning: considerations before adding a child patent to your portfolio

Child patent applications are valuable tools for building a patent portfolio that protects core technologies yet is adaptable to market pressures. Like actual children, child patents require careful monitoring and strategic action to reap the best results. Applicants should consider which child application strategies to employ when developing a robust patent portfolio.

 

A layered approach

One approach is to structure your patent family in a layered approach. The first patent in the family could be focused on core technology, while the child patents cover supporting features. For example, the first patent in a robotics patent portfolio may cover the physical arrangement of components in the device. The applicant could then file a child patent to cover the sensor fusion system, a child patent to cover the AI control model, and another child patent to cover the power management system. By filing a collection of child patents of varying scope, an applicant can increase the likelihood that competitors will infringe on their IP and decrease the chance that all of their patents around core technologies will be invalidated in a single court proceeding.  

 

Responding to evolving markets and competitive pressures

The pace of innovation and interdisciplinary collaboration often means competing products are introduced while an applicant’s patents for core technologies are still pending. A child patent covering a specific aspect of an invention can be a critical defense against a competitor’s efforts to design around a patent.

 

Maximizing patent coverage

A child patent may protect product features that address unforeseen market demand. While all patents in a family will expire based on the earliest priority date (barring patent term adjustments), strategically filed continuations can provide extended market exclusivity by covering new implementations of the core technology that emerge later in the product lifecycle.


Three child patent pitfalls

 

Why this matters for your business

Child patents are a powerful tool for protecting your intellectual property. The flexibility offered to inventors when building a patent family enables sophisticated offensive and defensive strategies. Child patents are especially valuable for inventors in the rapidly developing AI, robotics, and semiconductor fields. Inventors can build robust patent portfolios by strategically filing child applications to expand their patent family. By understanding the different types of child applications, vigilantly monitoring deadlines, and strategically drafting applications, IP professionals can build flexible patent portfolios that protect current technology and respond to market pressures.

 

At Bright-Line IP, we've helped clients, from startups to multinational corporations, maximize the value of their innovations by strategically developing patent portfolios.

 

Whether you're looking to protect a groundbreaking technology or secure your market position in key countries, we're here to guide you every step of the way.

 

Ready to expand your patent family? Contact Bright-Line IP today to discuss developing a winning patent portfolio.

 

Sources:

2.     United States Patent & Trademark Office, Fee Schedule, https://www.uspto.gov/learning-and-resources/fees-and-payment/uspto-fee-schedule (current as of 3/20/2025).

7.     Immersion Corp. v. HTC Corp., 826 F.3d 1357 (Fed. Cir. 2016).https://casetext.com/case/immersion-corp-v-htc-corp-4

 

 

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