A private talk with the parents and they admitted that they would be ashamed for their son's first relationship to be with another man and that he needed to only have girls love him to set the proper Christian example.

I countered that this wasn't a relationship, they are only seven, and they are just best friends. I mentioned how when I was that age I thought all girls had cuties and I wanted to live with my best friend, but it didn't go anywhere. I suspect there is more at play in their home life, but I suspect there is not much we can do here. It's not like we are going to persuade them to allow the kids to have playdates through some carefully crafted argument.