Brookie said,
I am thankful that he'll always have me. If he ever leaves the cult, or gets kicked out for not living up to God's standards, he'll have me - anytime.
I think it is very important that you tell him this and remind him of it from time to time as the years go by.
Long long ago, when my Mom became a Dub, she made sure that I had nothing to do with my grandparents, aunts, uncles and cousins. It was all her and the "new world society."
Many many years later, I contacted my remaining autns, uncles and cousins (grandparents had died), and guess what? There was no "emotional context" between us. Imagine that. We were like neighbors, not family; cordial and polite but unconcerned.
You can spare your nephew this fate. In eight to ten years he will need you, because that is when he will begin to realize that whatever dreams he has for himself will not be permitted to come true - unless his parents go apostate by then.