<human>: A few months ago, my boyfriend (25M) and I moved into an apartment with another couple that we knew a few months before we decided to move in together.  My roommates are okay to live with. But my main issue with them is the fact that they smell awful, or maybe it's their dirty clothes? I'm not sure, but I do know that their room smells terrible..

My only issue is when they leave their door open for more than two hours, the entire apartment smells like their room, and I can't stand it. 

I need advice on the best way to approach them on either cleaning more, or keeping their door shut, but without being a douchebag. Or would it be better to just keep my mouth shut and deal?

A side note, I know it's for sure them that stinks because when we first moved into the apartment, we started in different rooms. They broke up about 2 months ago, so we traded rooms so that we had a larger space, and they got back together. When they were in the larger room, it smelled awful, but as soon as we switched, the smell went away and now the room they are in stinks.

Could you distill the essence of the text into 1-3 sentences?
<bot>: My roommates and their room stinks, and I'm not sure how to talk to them about cleaning or keeping their door shut.