Sure, you already have siblings that means worlds to you but gaining another one is so so precious. You gain a new best friend, a new brother, a new protector.
You have more inside jokes than your boyfriend. You have a defender, when you're boyfriend is wrong.
Whether or not you and your bf last, you will always have a special place for his lil brother, who is your lil brother. When he starts dating, you'll be protective. AND IF SHE BREAKS HIS HEART YOU'LL HAVE TO TAKE CARE OF HER.
I love you Alec, my new little brother!