How old is he?

My female cat, Samba, also cries. She does it at night and her crying
goes on for half an hour or more some nights. I worry that it is
bothering the neighbours via the adjoining walls but so far no one has
complained.

It's not every night though. Sometimes, it _is_ every night for several
weeks but sometimes she'll go several weeks without crying.

I've never figured out for sure what causes it but I _suspect_ that she
wants to play. She seems to be quite lively when I go to bed. I once
tried playing with her at bedtime and she was quite enthusiastic. But I
didn't want that to become a habit for us; that would just tend to wake
ME up and make it harder for me to fall asleep!

You could try playing with your cat when he starts crying and see if
that helps the situation.

--
Rhino