Narcissistic Brother

Some of you may remember a few posts about my familly situation and how they just ignore most of the things happening around.

Well, also, i tend to write a few things about my brother and how we used to get along but now he acts like he doesn't give a single crap.

Well, long story short, he's in medicine school and there, he met his girlfriend, but both will be very occupied next semester.
I noticed he was both saddened and worried when he couldn't go back earlier to see her (We're from other city than her and the school).
I chatted with his grilfriend and told her that everything would be fine and i would keep an eye on him (Just to give her the assurance), but in the end, my brother is not an ******* around girls.
I told him this and that i could help him in any way i could... and, guess what
He told me that he was never worried at all, and that everything was on my mind, SO... i told him that even if he ever feels down, i could listen to him, AND... He said something like "I'm never down in situations like this, i'm a grown man, it is you the one who upsets more often, you shold have grown up already". This comment was really getting on my nerves, so i said something like... "Well, i'm some stuff i can be more assertive, in some others you are" and his final coment was something like "That's the point, i'm better at everything", so i just decided to leave him talking.

Hell, i offer him my help just to remember how crappy he can be around those who he take for granted, even to worry about his relationship. His grilfriend is a really nice girl and it kinda worries me that onec he take her for granted (Something tells me he will unfourtunely), he will show his true self to her.

Thank you, have a nice day
Any insight people?