Is there an extension to the stable roommates problem with multiple roommates per room?
Switching from 2 to 3 "beds" makes the problem NP-complete :-)

See K. Iwama, S. Miyazaki, and K. Okamoto, "Stable roommates problem with triple rooms." Proc. 10th KOREA-JAPAN Joint Workshop on Algorithms and Computation (WAAC 2007), pp. 105–112, 2007

(an electronic edition can be downloaded from ResearchGate).

Abstract: In the stable roommates problem, we are given 2N men and each person's preference list. We are asked to find a stable matching, namely, a set of N pairs satisfying the stability condition. This problem is known to be solved in polynomial time; more precisely, there is a polynomial-time algorithm to find a stable matching for a given instance, or to report that a given instance has no stable matching. In this paper, we extend this problem into three-dimension, i.e., a matching is defined to be a set of triples, and show that this problem is NP-complete. ...

See also this survey: Kazuo Iwama and Shuichi Miyazaki. 2008. A Survey of the Stable Marriage Problem and Its Variants. In Proceedings of the International Conference on Informatics Education and Research for Knowledge-Circulating Society (icks 2008) (ICKS '08). IEEE Computer Society, Washington, DC, USA, 131-136.