Is this normal behaviour?!

[whitewolf84]

I have a 4 year old daughter....I also have a 7 year old stepson who we see every other weekend as he lives quite far away.

About 2 months ago, my stepson and my daughter were playing in the next room when I heard my daughter say she 'didn't want to'...she then came over loudly, to say that my stepson had asked her to remove her trousers and pants...we've taught her the nspcc pants rule so she did well to make herself heard! we spoke to my stepson and just said that her underwear is private and not to ask this again. he understood. we spoke with his mum, who then spoke to my stepson and she said she was confident he wouldn't do anything like it again.
yesterday, whilst at my inlaws, i was feeding my new baby...and my husband was with his parents...my daughter came running in to say that my stepson had again asked her to remove her trousers and pants, but asked if she would keep it a secret.

i understand that children have interest in the opposite....anatomy....but how normal is this behaviour?! aibu to feel quite upset about this?!

I am wondering if the new baby has got him thinking about where babies come from etc? Has he any knowledge of things?? Maybe an age appropriate book if dh is too chicken for the talk just yet?

completely normal, but he has disobeyed instructions, and he knows you don't want him to do this, so swift and severe consequences for disobedience... is he normally disobedient?

a book is probably a really good idea, actually - thank you for the suggestion. he has two young female cousins too, that he spends lots of time with...he does have lots of little girls around him.
and yes, he is frequently disobedient! he's often in trouble at school (exclusions, detentions, etc) his mother wants him evaluated for adhd...
that said, he tends to behave pretty well when he's with us (albeit...a little headstrong at times)
for the time being i won't let them play unsupervised...daughter has mentioned it a couple of times today...i hope she wouldn't mention it at school and for the teachers to get wrong end of the stick?!