Well DS1 and DS2 started to share a room when I had DS3, they were 4 and 2 at the time. Their sleep was disrupted for about the first month after moving in together as DS2 was an early riser and DS1 liked to sleep but was woken by DS2. After the first month of ajustment they settle back into their routines and it didn't worry them.

Now we have had DS4 we have the three older boys in one room without much disturbances between them.

Advice I have is that it will be hard for maybe the first month or so until the novelty wears off then they will settle into either a new routine or their old one. HTH.

hugs xoxo