Concerning any wife who left their husband for their own brother, ....?

Tell them this: "I am a scumbag and you should not be in my custody"

Wait a minute ... your wife left you for HER brother, or for YOUR brother? The way your question is worded it is difficult to tell. Assuming she left for YOUR brother, what a hohohoho-cake. Who could do something like that when they have children in the mix? And geesh, what the hell does that say about the asshat known as your Bro, who could take his own sibling's poon, and smash it? It's facked up, man. You would definitely get a direct ticket to Jerry Springer with this shitsky.

It is depend on situation.

If her brother are need your wife help and there is no one to save his life, then it is acceptable and you shall bear all caring of kids and house work untill her return.

Otherwise, ask her come back or divorce her if she will prefer continue stay with her brother.

If possible, don't mention he is your brother until the kids are old enough.

Whose husband and whose brother? Your pronouns need work.