Gin, the 3rd Division Captain, seems like a kind, sort of playful person, but because he's uncaring when it comes to the troubles of others, and because of his occasional use of sarcasm, he is distrusted by many. Gin seems to have emotions (demonstrated by his reactions towards Rangiku), but he lacks an understanding and a desire to understand about others, and is generally self-centered. His loyalties do fall heavily with Aizen, however, and this makes me believe that Aizen is the one person aside from himself that Gin cares for (may you consider it friendship or otherwise ^_~)

Aizen's personality is even more of a mirage than Gin's is. He is quite easy-going and even could be considered soft spoken, and is especially kind to his subordinates. In truth, he cares not at all for them and considers them all of his pawns. He is not bound by morals and thus will stop at nothing when it comes to achieving his goals. In addition to that, he manipulates many, including his enemies, into helping him achieve these goals.

Aizen and Gin have shared a close-knit relationship for quite some time. Gin, at one point in time, was Aizen's vice captain and Aizen has made it apparent that he considers no one else other than Gin to be as such--this is expressed to the point that Gin is his "partner in crime", so to speak, when Aizen launches his plan to destroy Soul Society (or whatever his crazy little brain intends to do). Their loyalty is rather endearing to me, and I see these two being rather close outside of their professional relationship boundaries.