Lucy Solie-Vilker
October 29, 2026
Many families who build their family with donor eggs start thinking about a second child before the first is even born. One of the most common questions is whether a future brother or sister can come from the same egg donor, and a sibling cycle is one way to make that happen.
If you are planning ahead or already hoping for another baby, this guide explains what a sibling cycle is, how it compares with freezing extra embryos or reserving more frozen eggs, and what to think about before you ask your donor to cycle again.
The short answer
A sibling cycle is a second egg donation cycle with the same donor who helped create your first embryos.
Intended parents request one to have a child genetically related to their first, or to try again after a cycle that did not lead to a pregnancy. It depends on the donor's availability, willingness and updated screening.
What is a sibling cycle?
A sibling cycle is a repeat fresh donation cycle in which an egg donor you have already worked with goes through stimulation and retrieval again for your family. The eggs from that second retrieval are fertilized at your clinic to create new embryos, and any children born from them share the same genetic donor as your first child.
In the Donor Nexus Fresh Matching Program, a donor is matched to one set of intended parents, and the donor works with your clinic. A sibling cycle follows the same process as the first cycle, with one advantage: you, your doctor and the donor already know how her body responded to the medications.
Why do intended parents choose a sibling cycle?
Most parents request a sibling cycle for one of two reasons. Some had a successful first cycle and have used or run out of embryos, and they want their children to share the same genetic background. Others had a first cycle that did not result in a pregnancy and still feel their donor is the right fit.
A cycle can fall short for many reasons, including embryos that do not develop, embryos that are chromosomally abnormal, or a transfer that does not implant. Your doctor can help you understand what happened and whether the donor's response makes a second cycle reasonable. Parents often come back to the same donor because the connection they felt to her profile has not changed.
What are your options for siblings from the same egg donor?
You have three main paths to genetic siblings from one donor, and many families combine them.
| Option | How it works | What to consider |
|---|---|---|
| Freeze extra embryos | Extra embryos from your first cycle are frozen for a future transfer | Often the simplest path when the first cycle produced several good-quality embryos |
| Sibling cycle | The same donor completes a new fresh cycle for your family | Depends on donor availability, updated screening, new costs and her remaining cycle limit |
| Another frozen egg cohort | You reserve more of the same donor's eggs from the Frozen Egg Bank | Only possible if that donor has frozen eggs still available |
Our comparison of fresh vs frozen donor eggs looks at how each program affects egg counts and planning for siblings.
How many embryos can one donor cycle create?
One fresh cycle can create enough embryos for more than one child, although results vary from cycle to cycle. Across Donor Nexus fresh cycles from 2012 to 2025, donors averaged 28.9 eggs retrieved, 22.6 mature eggs and 18.2 eggs fertilized through ICSI. Where PGT-A testing was performed, cycles averaged 7.2 euploid (chromosomally normal) embryos.
Those numbers matter because most transfers today use one embryo at a time. The American Society for Reproductive Medicine (ASRM) recommends that transfer of a euploid embryo be limited to one, regardless of patient age, and that single-embryo transfer be planned in donor egg cycles when the donor is under 38 and other factors are favorable.1 Transferring one embryo at a time lowers the risk of twins, and it can leave remaining embryos frozen for later.
Frozen eggs work differently. A Donor Nexus Frozen Egg Bank cohort includes 6 eggs, and in our data 81.1% of cohorts produced at least one blastocyst and 60.5% produced two or more. Families hoping for more than one child sometimes reserve an additional cohort from the same donor when eggs are available.
What should you know before planning a sibling cycle?
Before you request a sibling cycle, talk through availability, screening, timing, cost and how many cycles your donor has left.
Your donor's availability and choice
A sibling cycle is always the donor's decision. Life changes, and a donor who was available two years ago may now be pregnant, working in a new city or no longer donating. Our post on what happens when an egg donor backs out of a cycle covers how agencies handle changes in plans.
Updated screening
Every new cycle requires current infectious disease testing. Under FDA rules, the blood specimen for an egg donor's infectious disease testing must be collected close to the time of retrieval, no earlier than 30 days before it, so results from your first cycle cannot be reused.2 Your clinic will also review any changes in her health since the last cycle.
Timing and cycle limits
Your donor will be older at a sibling cycle than she was the first time, which is one reason families who want siblings often plan early. ASRM recommends that egg donors be limited to six donation cycles, counting cycles she completed for any family.3
Costs
A sibling cycle is a new cycle, with new donor compensation, clinic, medication and legal costs. Donors set their own compensation, and returning donors may ask for more on a later cycle. You can review typical costs on our financial breakdown page.
Will the children be genetic siblings?
Yes, children conceived from the same donor's eggs share her genetic contribution, and they are full genetic siblings when the same sperm source is used for both. If the sperm source is different, they are half siblings.
Children from your donor may also have genetic half siblings in other families if she has donated before or donates again. Our guide to donor-related siblings explains how some families choose to connect.
If a sibling cycle or another cohort is not possible, your children can still grow up as siblings in every way that shapes a family, and some families choose a new donor for a second child. Browsing the Donor Nexus donor database is a good way to see which donors have frozen eggs available today.
If you're exploring donor eggs, our guides to using donor eggs, how our egg donor agency works and our frozen donor egg bank walk through each path, and you can create an account to search the egg donor database whenever you're ready.
Frequently asked questions
What is a sibling cycle with donor eggs?
A sibling cycle is a second egg donation cycle with the same donor who helped create your first embryos. Parents usually request one to have a genetically related sibling or to try again after an unsuccessful first cycle.
Can you use the same egg donor twice?
Often, yes, if the donor is still available, willing and medically cleared. She will need updated screening before a new cycle, and ASRM recommends that egg donors complete no more than six cycles.
Will my children be full siblings if we use the same egg donor?
Children conceived with eggs from the same donor and sperm from the same source are full genetic siblings. If the sperm source differs, they are half siblings.
Is it better to freeze extra embryos or plan a sibling cycle?
When a first cycle produces extra good-quality embryos, freezing them is often the simplest path to a sibling. A sibling cycle is an option when no embryos remain or when you want more to work with.
Can I buy more frozen eggs from the same donor later?
Sometimes. If your donor has additional frozen eggs available in the Donor Nexus Frozen Egg Bank, another cohort can be reserved, but availability is limited and not guaranteed.
Sources
- Practice Committee of the American Society for Reproductive Medicine and the Practice Committee for the Society for Assisted Reproductive Technology. Guidance on the limits to the number of embryos to transfer: a committee opinion. Fertility and Sterility. 2021;116:651-654. asrm.org
- U.S. Food and Drug Administration. 21 CFR 1271.80, What are the general requirements for donor testing? Electronic Code of Federal Regulations. ecfr.gov
- Practice Committee of the American Society for Reproductive Medicine and Practice Committee for the Society for Assisted Reproductive Technology. Guidance regarding gamete and embryo donation. Fertility and Sterility. 2024;122:799-813. asrm.org
Medical disclaimer
This article is general information about donor egg sibling cycles and is not medical or legal advice. Talk with your fertility doctor about embryo planning and with your attorney about any agreement for a future cycle.
Related reading
Lucy Solie-Vilker
Lucy Solie-Vilker is the CEO of Donor Nexus, where she's helped build one of the most established platforms in egg and embryo donation. Since 2012, her work has contributed to more than 2,000 babies born to Don…
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