Sounds like a bit of separation anxiety
He's at the age where it should be starting (somewhere around 6-9 months, sometimes a little later). For some it hits harder than others. The most you can do I'm afraid is whether through it.
Something you could try though is setting up a pack n play/playpen (the one he sleeps in at grandma's) at home and have him get use to sleeping in it at home (assuming you have one). Have him sleep in it a few nights, then a few nights in his normal bed/crib, then back in the playpen for a few nights. When you think he's use to it, put the playpen in a different room, and have him sleep in it there for a few nights. That way, if he refuses to sleep in it, you can always move him back to his normal bed (but try and keep at it different nights).
This really helped my lo. She use to be that way at grandma's house (both of them). Now she takes 1.5-2 hour naps at both houses after we practiced at home. We don't get out to see the grandparents very often, so the practice at home really helps her.
Hope this helps!
*HUGS*
Sonya =P
