7 year old neighbor boy has been playing "secret touch" with my 5 year old son

It came out recently that a 7 year old neighbor boy who regularly plays with our 5 year old son, had a game of "secret touch" where the 5 year old would pull down his pants and the 7 year old would touch his penis. This has apprently been happening for a couple months.​It came out when my 9 year old daughter visited that same house and the 7-yr old said she couldn't go to the bathroom unless he could watch and she fought back. Then the 5-year old shared the "secret" with his older sister.​I know kids mess around a bit with this kind of stuff, but this is beyond normal messing around levels.​We've talked to his parents. We're not ending the friendship, but they don't get to play inside anymore.​I'm curious if a 5 year old may need any other support or help with something like this? On one hand, I don't want this to fell like a big deal to him. We've talked about how people shouldn't get to touch you in swimsuit zone and how people who tell you to keep secrets from mom and dad are just trying to do bad things. He's fairly nonchalant about the whole thing so far.​And I don't know how much he'll remember as a 5 year old. But I also don't want him to carry some kind of burden of having broken a secret or done something wrong or even just normalizing behavior that probably shouldn't be normalized.​I know the reddit reflex is always "get a counselor", but I'm not sure if that would make the situation better (by helping him figure this out) or make it worse (by cementing it in his head as a significant event). via /r/Parenting http://bit.ly/2Mn8VwT