I'm also surprised at some of the responses you're getting.
As I see it, you have to think of your family and your kids first. If that means alienating family then so be it. Your kids come first and you want to protect your kids as long as possible. Let them remain kids as long as possible.
The problem, as I see it, is we've been desensitized in so many, many ways. Because of this, doing the right thing or even mentioning it will make us look like we're from another planet to some people. In all things I am a Christian first, so in that sense coming across as if I'm from another planet doesn't bother me because of what the Bible says in regards to those who belong to Christ.
There's no need to be rude or hostile. Treat this family member as Jesus would. Love them. Tell them the truth. At the same time, keep your kids away.
“Love them. Tell them the truth. At the same time, keep your kids away.”
Wise response.
“...There’s no need to be rude or hostile. Treat this family member as Jesus would. Love them. Tell them the truth. At the same time, keep your kids away...”
That is the answer in a nutshell.
Excellent advice.