So at the epilogue They had a daughter(Cassie) and a Dog(name Vicky)
Now where did they get the dog? In chapter 11(In Plain Sights) After the Lemur stole Nate's apple he had a conversation with sully it went like this
Nate: Hey you know what after this, I'm gonna get a dog
Sully: Hey, if we come out of this in one piece, I'll buy you the damn dog
Nate: Can I name it Victor?
Sully
Laugh) Sure
Noticed this during my second play through the dog was a girl so they just called her Vicky instead.. this game is so beautiful so sad that it's over.
Also Cassie was named after his mom.. the feels