My boys share they are almost 5 and 4. We had them seperate until around a year ago. There’s no way they would have slept well sleeping in the same room before that. So I’d say seperate them until bub is older. Have a night light in each of their rooms and let your 3 year old pick out a special cuddly to sleep with so he doesn’t feel so lonely.
Published 23rd September 2019