The layer list is not fully scrollable in the moble version. Since the family layer option is the last one, I simply couldn’t scroll far enough.
Now everything is working, but I’d recommend to fix the css.
Edit:
It’s not 100% reproducible. Sometimes scrolling works, sometimes not.
But I have a reproducible bug/problem:
It takes quite a while until the family members appear on the map after activating the layer and the tick doesn’t stay ticked. You have to reactivate the layer after each reload.