All my kids love bathing together, all squished in. 8yr old DD, 6yr old DS...and the younger girls, all don't care at all. SOMETIMES i'd say in the last 6 months, 8yr old DD will opt to take her own bath, but often still hops in with the others.
If 2 yr old DD grabs at my DS's penis, which she does sometimes, it seems to be endlessly funny for all of them, and then he tells her to stop. I would always help him if he wanted me to.
It just has never been an issue for them and If it was, then I feel confidant they would change things.
Bath time is a time they really enjoy all together.
Any of them sometimes bath with me as well, although 8yr old doesn't fit so well, and gets a little grumpy. those days seem to be over.... I also notice DS has pretty much stopped getting in with me too, probably younger because of the gender thing and because he has always been more modest...(DP is more modest than myself, so he definitely
follows his model somewhat)
I always bathed with my siblings and remember my sister hoping into the shower with me in high school once because i was taking too long, laughing hysterically.
totally her sense of humor.