But SHE has moved back with her family including a boy who looks so remarkably like my husband that people are starting to stare if not outright talk. I'm not sure what to do, especially because my husband doesn't want to talk about it.
maybe take a cue from the not-acting-slutty-but-honest-and-s incere-behaving other woman. talk to the boy, talk to the mom, talk to your husband- weather he talks back or not. sounds like in a certain way there is another member of your family near by. might as well face it, embrace it, be kind, be honest. looking at something as a scandal is for the shallow. it can not be undone. who knows, with an open heart this boy might be a lovely part of your lives some how. if people gossip just walk proud. shame is for people who have no creative perspective on that which they can not controll. Invite the kid to dinner. it will undoubetedly be complecated but who knows- there can be great power in unexpected generosity of heart.
Leave it alone, the kids got a mother and a father, they are all he knows, just because he looks like your husband don't mean a thing. Your husband and you know he had a relationship, you both know it could be his, you could have done the same thing. If you get this started you might just get hit with a very large back child support bill.
This looks like a problem which won't go away.
I suggest you insist your husband and you deal with this situation.
It'll just make your lives miserable in the background if you try to ignore it.
how old is the boy