For the best sleep as a couple, you need a bed with ample space. 90 cm per person is a sensible rule of thumb, but a little less can also do it.
When a couple sleeps tightly in a bed, the springs and foam are compressed more than if a single person were lying in bed. It impairs the adaptability of a mattress and has the consequence that you no longer get the support that a mattress should provide.
In JYSK, we therefore recommend a mattress or bed of 160 cm or 180 cm in width for couples.