When couples suffer from infertility or an inability to have children, they often turn to surrogacy as an option. For example, gay male couples may decide to get a surrogate mother to provide them with a child that they can raise on their own. You and your husband went this route and chose his understanding sister to be your surrogate.
Unfortunately, your husband's sister is suddenly claiming that she wants the child because she developed a real connection with it. Even worse, she is starting to bad mouth you and your husband and claiming that she won't give up the child after it is born.
This situation can be very complex without a lot of help. Gay parent surrogacy rights can be very confusing and may be problematic in some states. For example, some areas of the country still frown on gay parenting and may wish to give the child to the mother instead of a happy and stable gay couple.
It all depends on what kind of rules and regulations your state puts into place. For example, some states require that a couple adopts a child after surrogacy, even if your sperm was used to impregnate your husband's sister. In this scenario, she may try to deny you those adoption rights simply because you are gay.
Thankfully, the fact that you are the father of the child won't be ignored by courts. Just as importantly, your legally-binding agreement with the mother will be brought up during a court session. If she is trying to back out on this type of agreement, there is a good chance that her case will be useless and that you will retain rights of your child.
That's why defending your rights requires contacting a high-quality family attorney who will work to ensure that you and your husband get your child. They will go over your agreement and find the clauses that ensure you get your child. Even better, they will argue for your parentage and claim that you have just as much right to the child as the mother.
You need to contact a family law lawyer as soon as possible, perhaps even before your husband's sister starts acting weird. This can help you be prepared for the possibility that she may try to claim the child as her own. Hopefully, you and your husband don't have to go through that, but if you do you can be prepared.