I Guess I Was Moreso Stating That is Why I Would Feel Guilty.
I Know Its not a WRONG thing to Do if You Have to.
I Would Feel that if We Had 2 Bedrooms , The Kids shouldn't all have To sleep together.
Again , this is My Feelings , and Maybe why OP said she felt guilty To Begin with. IDK -

I Have NO problems With Kids sharing Rooms. I Don't Need You all telling Me how Great your Kids Turned out Sharing a Bedroom - LOL- I Know It Can work.
I Knew A Girl who had to Share a Bed with her Sister.

We Only Had 3 bedrooms and We Had 3 kids and I Kept our Girl in with Us. though. I would've felt Guilty , Just sticking her in with Her Brother ,It wasen't a Big Deal with Her in our Room For a Couple Yrs. till we Bought a Bigger Place.

How Does Your Older 10 Yr. old Feel about having 3 Sibs in his Room?