K.H.
I don't know much about potty training (my son is only 10 months old and not yet ready) I do however have some advice on the sibling thing. I think it would be a great idea to get him a baby doll. Little boys love to do what thier moms do just as much as little girls. You can even get a boy gender doll if you are uncomfortable with the notion of a baby doll (Im not saying you are but some parents don't like the idea). You can help him to learn how to be a big brother and at the same time you are teaching him skills that will help him become a great father. Just let him do with the baby doll what you would do with the real baby. You can start now so that when his brother comes he will be ready.