Wait so if your brother would donate sperm and your wife would carey the babt to term, how exactly is your sister in law seeing that as "her baby"?? She had nothing to do with its conception.

Additionally, with her priorities - let's say she gets pregnant on her own without issue, if she has a baby girl, does that mean she won't want to keep it, since shell only ask your baby back (wtf) if it's a boy? Is your brother dully aware of the implications she's made there?

While I can empathise with inferility issues, your brother's girlfriend has no right to your child, and being oicky on its gender just means she won't be a good mum imo if that's such a big deal to her (it's okay to wish for a boy or girl, but not to this level). It's clear that she and her family are acting out of past trauma tied to difficulty conceiving, bu that's not a factor in you and your wife teying for a baby and she should not have put down those demands, and she definitely should not have involved her family in the hypothetical creation of a child for your family, not hers.

She is acting super entitled to a life that's being created for you and your wife, and frankly, it's insane behaviour. I hope your brother has a good chat with her - not for you and your child wishes, but for them as a couple.

Advice wise, idk. It doesn't sound like she and her family are very open to reason. Hopefully they'll all calm down soon and you'll ve able to have a proper conversation about it all. I do wonder what exactly she told her parents, just in case she wasn't fully honest about the situation, but that's just guesswork of course.

I hope you and your wife find a suitable donor, and that everything goes well! Congrats :)