9 year old son and his bears

In the past week, my son has began to play with his bears as if they were babies.

He dresses them, puts them to sleep, changes their diapers and ever refers to them as my grandbears. Lol

I figure its a phase because he has a 10 month old new sister and he’s seen and helped with how we care for her.

Has anyone else’s son done this or similar?