When Should Two Brothers Stop Taking Bath Time Together

When is the best age(s) to stop letting your kids take a bath together?

Now right now I'm talking about the same sex of course. When I was little I and my sisters used to take a bath together. My sister even took baths with my cousins at my grandmother’s house. We were all girls. All six of us.

Right now, I have 2 boys. They've been taking baths together since my youngest could stand on his own without falling too much. Right now they're 8 & 6 (turning 7 in a few weeks). They still take baths together. In my part it's more to conserve on water. They've taken baths on their own once in a while when one wants to take a bath and the other doesn't want to at that time. But for the most part, about 80% of the time they take baths together.

My oldest boy is getting older and I don't know when I should start making him take a bath on his own. Should I wait until he tells me himself? My bathtub isn't that big, pretty small actually. When they start to fight in the tub of course I threaten but they like playing together, they're kids.