This is what some say. I’ve heard people asking if there is a recommended age you stop bathing different sex siblings together.
My kids are still all very young so I don’t think I’ll be crossing that bridge for a while. I think as long as they feel comfortable and there are absolutely no signs of pubity I don’t mind it. However with the world we live in today and the things kids are exposed to getting out of control it won’t surprise me if I think differently once I actually get there.