Caught my nephew sucking on nipples?

[Bethel4]

I’m completely at a loss. I found my 10 year old nephew (boy) sucking on my 6 year old (boy) nipples. After talking to them I found out my nephew likes to kiss my son also? Never thought anything like this would happen. Is this normal behavior? What do we do?

[Sandman2]

While sexual exploration is common with 10 years olds.  It is not when it is between a 6 and 10 year old.   and both of them need to know this is not acceptable.  I would not leave your nephew alone with your child.  I would also get a book such as "I said No"  https://www.amazon.com/Said-Guide-Keeping-Private-Parts/dp/1878076493/ref=sr_1_1?ie=UTF8&qid=1531980176&sr=8-1&keywords=private+parts+book+for+kids

and read it with you son.  And there are several other good books listed on the site above.