I really wouldn't worry too much yet hun, I was a little worried about Thomas a while back as he sounds exactly like C - great away from home but extremely possessive within his own environment.
Anyway I have been reading a book recently that makes a hell of a lot of sense - 'How not to F*** them up' by Oliver James. He is a child psychologist and is adamant that children under 3 don't need to socialise with children their own age and are much more comfortable in the company of adults and older children. He also says that children under 3 are mentally incapable of sharing (understanding the concept) they can be taught to hand things over but they wont understand why and will generally get upset.
I was initially skeptical as I'm not usually into books but I have noticed in the last week or so that Thomas is actually starting to pick up on my stressing the 'sharing' thing with Hannah. He initially objects but then corrects himself and says 'no no must share with baby' and gives her the disputed item (only allows her 5 seconds access and wants it back but its progress and shows he is learning
). He will be 3 in 5 weeks so maybe there is something in it?
The problem I have now (and you will have soon too) is having one toddler that will attempt to share and one that can't (too young) - STRESS!!!
xx