Brawls happen everywhere. Even in the fanciest places.
Gangs also spring up everywhere - I remember being part of a 'gang' when I was at school and barely 7 yrs old. It was a group of friends, nothing more, but we called ourselves the Hells Angels.
It did NOT mean we were affiliated with the real Hells Angels, or even in reality knew what they were, it just sounded cool.
Lots of groups of young men style themselves on 'gangs' when they are in reality just groups of friends.

My concern in all of this is not whether or not these guys are or arent a gang, friends, dangerous, or teddy bears. Its more fundamental than that. If someone is too scared to meet his girlfriends family. - If his love for her does not transcend this most simple of boundaries it is NOT going to be long lasting.
People like this should grow some backbone and go and find out in person - you never find out what people're about while you hide behind a keyboard.