Greg responds...

Broadway is too old for Goliath to regard him as a Rookery-Son. And too young for Goliath to regard him as a Rookery-Brother. Now, without a doubt, Goliath regards Broadway as family, as part of his clan, as a cousin, as someone so close to being a "little brother" that it might not be unexpected for him (if he were human) to use the term.

But Gargoyles aren't humans. They don't use the term "little brother" to describe that relationship. Or any relationship, really.

And the word "friend" to a gargoyle carries real weight. It's not insignificant or casual.