During the New Mutants arc, and during the current arc. He's the older brother - he and Scott are totally estranged, Alex having turned down Charles' invitation to the Institute. Also, Alex is obsessed with Scott - there's a nice moment in issue 61 where Lorna >:0s at him for talking about his brother all the time. :D
Re: *heads to bed now, will continue this conversation should you choose to continue it, tomorrow*