In our home ed groups, where the children are not accustomed to being separated into age-groups, they play together in very mixed-age games from toddlers to the very early teens, and the rules become sort of automatically adapted to suit the different abilities. They do also play in similar-stage-of-development groups, but it's not a big deal either way.

What astonishes me is siblings who enjoy and seek out each others' company. That makes me choke up.