•Sasuke is of course shocked. He doesn’t know how to feel about it at first. Maybe he’s angry? Maybe he’s relieved? Maybe he’s happy? Like wow, he has nieces and nephews. A sister-in-law. The kids have Uchiha blood. He’s not the only Uchiha left wow. How does he feel????
•Assuming he knew about the truth behind Itachi’s death already, and he doesn’t hold any of that animosity for Itachi anymore, Sasuke won’t treat the wife and kids with any hostility
•If they didn’t already know the news of Itachi’s death, Sasuke would break it to the wife in private. Like, it all depends on the context. Do the kids know they’re Itachi Uchiha’s children? Or did the wife keep it from them to protect them? Does the wife know why Itachi had to do what he did and abandon the village? Sasuke probably won’t fill her in if she doesn’t know. He’ll want to. He’ll want to tell her that her husband Itachi was a good man and not what Konoha painted him to be, but I just don’t think Sasuke would. Maybe that’s just me
•Sasuke might want a relationship with his niece/nephew(s). It just depends. Maybe later on once he’s dealt with his “vengeance against Konoha” deal. But I can see him wanting to be there for Uchiha children growing up without a mentor (assuming the mother wasn’t Uchiha herself)
•On the other hand, he might just leave them be. At least he knows that Itachi had a family and probably found some happiness there. Maybe Sasuke doesn’t want to get Itachi’s family involved in any drama that surrounds the village and the Uchiha massacre. So he might just drop by, see it for himself that Itachi had a family, and then be on his way. He won’t tell anyone about it. If they need help and want to relocate somewhere else then sure, Sasuke would help. He’ll even send money or supplies to them every month if they need it. But otherwise, he’ll leave them be