My 2 yr old is very touchy

Can someone give me some insight. So my 2 yr old and my 16 month old nephew were playing together and all of a sudden it got quiet so I look over at them and my son is petting/rubbing my nephews belly, poking nephews belly button and just overall being touchy. I told him not to do that and just prompted them to continue playing and was wondering if being touchy is normal? He once caressed my SIL leg and touched our hooters waitress legging once but other wise he’s pretty normal, me and husband aren’t really affectionate in front of him so it’s not like he watches us and I’m a SAHM so no one is showing him this lol. He does sleep in our room so maybe sometimes he’s woken up while we’re “busy” but we stop when he wakes up usually. He also likes to smack our butts when we get out of the shower. Is this normal toddler stuff? Worries me