It's one thing to say "Don't bring your casual flings and hookups around my kids when you're one of their main non-parental caregivers"

I actually think that given the number of hours of free childcare he's getting, and the fact that it sounds like the free childcare is coming out of the brother's leisure time, this might actually be an unreasonable ask - and I would not blame the brother at all if he said "Your choices are free childcare with whoever I'm dating tagging along with us; or an end to free childcare"

Like, what is his plan if he tries to ban the brother bringing dates along to the beach and the brother says "Okay, I'm out, good luck finding a daycare!"