Friends are a little difficult for Collin, as he doesn't always understand the lines between them. Some friends it's okay to sleep with, some it isn't. Some friends will tell you their secrets, and some will tell his. He can't always tell the difference, so he tends to be a little withdrawn. If someone can get past that and deal with it, though, he's loyal until he dies.
He likes to think there aren't many enemies in his life, now that He Who Must Not Be Named was defeated. If he has any enemies now, he hopes they're there because of his personality, and not what he stands for.
Lovers are hard to quantify. Is a lover someone he's slept with? Because that would mean there are plenty. Is a lover someone that he feels deeply for? If that's true, he's never had one before. But wait, friendship could be felt deeply. Would that mean he'd had a few?
No matter the definition used, Collin doesn't keep lovers long. Eventually, they grow tired of his emotional distance and he lets them go because he isn't cruel enough to make them stay.