I don’t think there is any set age for any of these things. Each family is different, and everybody’s children are different as well. One poster in these responses even doesn’t allow tickling whatsoever in their family

eek

which is unimaginable to me! But, that’s to me and my family; not hers.

My point is simply that all families are different in these matters.
I personally don’t believe that we need to teach our children to be uncomfortable around one another. It is going to happen quite naturally. My parents never gave my brothers and I a talk about needing to stop bathing together, it just sort of stopped. Most likely, my brother wanted his privacy and didn’t want his little sister around to pester him. Now that I think about it, we always had separate rooms but I would frequently go to my oldest brother’s bedroom for advice, consolation, or just to hang out. I would fall asleep by him on his bed relatively often until he moved out of the house when he was 18. I never thought of it as inappropriate in any way… He’s my big brother. Heck, my oldest brother STILL tackles me to the ground when we get to see one another, and he’s 36.

Granted we can only see each other every few years, which
might merit such a joyful reaction to being brought back together.