I would suggest that your son is feeling somewhat neglected in the presence of his new sibling. I am sure you not intentionally doing it, but he has had you all to himself for his whole life, and how he has to share you with his sister. And, as infants usually require more time and attention, he may be feeling left in the dust with all the attention his sister is getting, like he just got moved down the totem pole.
What may ease things it to be sure to pay special attention to him when you can, like taking him out by himself, or doing something only with him. He will not yet appreciate that you have to be responsible and attentive to his sister as well, but it may make him feel like the center of attention again, even if just for a little while.
My daughter is 22 months, so we’re in the same place. She’s also starting to be defiant–running away from me is the new thing.
With her, these difficult behaviors have really been “phases” so far. Her phases last about two months, then the behavior subsides… or rather, she starts in on something else. So my advice is to cross your fingers that this is temporary, let your son know that what he’s doing isn’t acceptable, then try to use positive reinforcement to get him to do what you want. He probably isn’t going to be doing this constantly for the rest of his life
Just to hear myself type, I’ll share what my daughter’s phases have been: 16-18 months was frustration tantrums. 19-21 months was being afraid of many things, including sleeping.
It’s nice to hear that other people have gone through this as well. We’ll try and put at little discipline to him (via walking away) as well as spending as much time as we can with him.
So my now 22 month old just head butted my 10 week old. Actually he fell on her. She freaked, cried but seems to have calmed down. Now she is asleep. Of course I’m panicking that I should take her in to the ER.
