This has been a thing for us for a while. I used to suffer from really bad insomnia. My H needs his sleep and doesn't suffer from insomnia. I would keep him up, by moving around or reading etc and he'd get grumpy.
Also, I like night time. It's the only time I can truly relax alone.
I started sleeping on the sofa for some of the night, most nights really. If I could sleep, I stayed in bed of course.
Then I was pregnant and again, could not sleep. So I slept at least some of the night away from him.
Then I had a baby and didn't want to keep H up all night, so slept separately with baby.
Then pregnant again, same issue.
Now we have a baby and a toddler and I sleep with the baby, in order not to keep my H awake.
Baby has just turned six months, so I'm happy to move back into my bed, however has a terrible cough at the moment, so I need to stick around to make sure baby is OK.
Husband hates me for it.