There have not been many cases regarding the disposition of frozen embryos between partners. In fact, only about 10 or 12 cases exist. What is interesting about these cases, is that any agreements to give the embryos to one of the partners upon separation were struck down and agreements to kill the embryos were upheld.  The arguments to invalidate agreements range from a Constitutional right not to be a parent to invalidating agreements for very minor issues.  The caselaw is all over the place.  But one thing is certain, awarding embryos to a partner is almost an impossible task, even with an agreement.  Only in extreme cases, such as the most recent case in Illinois, does the court even consider granting custody to one of the partners.