My sister in law has a 4 year old daughter, whose biological father had nothing to do with for all this time, other than child support that he avoids paying. She recently called my husband and claimed that the father now wants to get primary custody to suposebly not pay child support, so to avoid that, she is asking for my husband to adopt her daughter ( just on paper because she plans on keeping full custody ). Is it me, or does this sound shady, because in order to adopt the biological father would have to sign over his rights, which why would he if he IS trying to get custody? And what exactly would that mean for my husband, can she take him for child support? It is not like she is signing over her rights, for some reason she just wants her brother to be listed as the father?. Is it me, or is there something odd about this?.

If he wants custody to stop paying support, you can pretty much bet that it is going to get thrown out of court.

The chances of your husband adopting the child to avoid a custody battle is also not good. I believe most states will not allow siblings to coparent a child anyway.

There is something very odd about this... like your SIL has no clue about custody, visitation, support and adoption.