I have two kids, a 3-year-old boy and a 16-month-old girl. They are in separate rooms right now, and it would be fine if they stayed that way. However, I shared rooms with my sister growing up some of the time, and while I hated it when we were older, I think I liked it when we were younger. I’ve heard people say there are statistical benefits to siblings sharing rooms. Is this true? Does it also make sleep for the kids better or worse?—Wondering How Much Sharing is Too Much
There is very little data on this question! There is at least some data on room sharing with parents, especially in younger infancy. But this question of room sharing with siblings as kids are older appears to be quite understudied.
Even on the most basic question of sleep, the data is limited. One paper from 2019 suggested that room sharing was correlated with taking longer to fall asleep, but in these data the authors conflate room sharing with a grown-up to room sharing with a sibling. Part of what makes answering this hard, as you might imagine, is that room sharing is closely correlated with other family features. Most families who have an option to put their children in different rooms do so, meaning that house size (which is reflective of income, location, etc.) is a big determinant. But, of course, these other family differences may also play a role in sleep.
On the broader topic of, say, whether sibling room sharing generates closeness or gives some other benefits, there is really nothing. The occasional dissertation with a few interviews, but nothing that would point systematically to say it is better or worse for kids.
I read this all as saying there is no strong data-based reason to do one thing or the other. Long-term, you will almost certainly want them in separate rooms, which may argue for keeping the status quo. Moving beds is hard.