To wonder if my 3.5 year old is ever going to leave his sister alone?

[Deerinthewood]

His sister is now 10 months so you’d think the novelty would have worn off a bit but it’s constant. She can’t play with toys or even just sit as he’s trying to sit on her or something stupid.

Has anyone else had this?

Put him behind a stair gate every time he goes to do it? You need to prevent the behaviour to break the habit. Hopefully she's not far off being able to play with him properly and then things should improve. Most likely it's attention seeking from him - presumably every time he sits on her, he gets a response from you.

It’s tricky because he can open and climb over stair gates fairly easily. Plus downstairs is a pain, it’s all open plan. It’s so stressful because I just can’t do anything. Dread the days were all together which is a shame as out of the house it’s all fine. I’m unsure whether it’s over exuberant affection or attempt to harm or a bit of both.