Don't bring it up. Their parents have a reasonable expectation that you're not going to try to de-convert their children when they're not around. If they ask, don't lie. When it does come up, report the conversation to their parents. It's important that they don't feel you're undermining them behind their backs, you don't want them to hear about the conversation from the kids first.
And your brother and sister should already know you're an atheist if you're contemplating explaining it to their children.
Take the high road all the way.
And your brother and sister should already know you're an atheist if you're contemplating explaining it to their children.
Take the high road all the way.
