It could be partially teething but i agree with Nise there just might be too much changes at once for him. He might feel a little jealous as well. He’s use to getting your guys attention. I read the best to help with that is try to give him one on one time too.
Aww I’m so sorry! I only have my one son so I can’t really say much but maybe he’s just in a little funk with all the little changes in such a short amount of time. I’m sure he will be back to normal soon. Congratulations on the little girl! 🎀