Border Collie behaviour

[chazza]

My boyfriend had a border collie from a pup for about 5 years before moving in with me.

The dog has a fantastic nature and I have a great relationship with it, he is very affectionate and playful with both my boyfriend and myself. He is very obedient when either of us tell him to do anything and as far as I can see, sees me as a master as well.

However, if we get too close, whether he puts his arm round me or I kiss him or whatever, the dog comes running over, gets as close to me as he can and stares at me intently, sometimes even starting to tremble and shake

Is this just jealousy that I'm too close to his master? Someone suggested it could be because the dog sees himself as the alpha male and therefore any female should be with him instead of any other, but this seems a bit far-fetched for me! Any other suggestions?