The birth of a sibling can be such a big transition for little ones. It’s also a time where we as parents can be stretched to our limits, meeting the round the clock needs of our newborn, and experiencing the resultant sleep deprivation.
As a result, it is really common to see some behaviour arising that can be challenging for parents – anger, aggression, not cooperating, acting “oppositional”, showing less independence, acting “clingy”, regressing in their development, or any combination of these!
Connected Play can be such a powerful tool in this scenario, and can be a really “efficient” way of filling a child’s cup with love and connection (that is, maximum impact in minimum time). It is a way of reassuring kids that they are seen, they are valued, and they are safe!
A game that is super-powered for this situation is called “He’s/She’s mine” game. Basically two caregivers (or a caregiver and close friend or relative) pretend that they both want the child so much that are willing to fight over him!
So one picks up the child playfully and runs away carrying them, saying, “He’s/She’s mine”. Then the other chases after them, and playfully wrestles the child from the person, hamming up how much they want them, saying “No! No! He’s/She’s mine!”.
It generally gets a lot of laughs from kids, so it helps to release lots of stress and tension, and the sense of connection between the child and caregivers gets a big boost. And the game can continue as long as everyone is laughing and having fun.

Playing this kind of connection-boosting game, even just once per week, has the power to turn children’s challenging behaviour after the birth of a sibling. In fact, this game can be helpful anytime there’s sibling rivalry between young kids (just not in the presence of the other child!).
Something else that is vital, and I know this is challenging when you have multiple kids, is to keep trying to make sure that we do things to fill our own cups and release our own stress, to nourish, ground and resource ourselves (including getting extra sleep, if necessary!).
This will help us to respond to our older kids with as much patience and loving kindness, as well as playfulness, as possible, acting as an anchor for them as they experience the veritable storm that the arrival of a new sibling can represent in their lives!