Aggressive rat

Hi, first time rat owner with 2 males that i have had for 5 months now. The bigger male is a biter that has bit since the day i bought them (they were bought as babies from a pet shop). I noticed from the day i got him he has never been interested in human interaction compared to his cage mate that enjoys being handled. He usually nibbles my finger but today i was stroking him and he seemed fine until he bit, harder than he usually would and drawing blood. He’s doesn’t appear fearful at all and it seems he just bites due to aggression. After spending the past 5 months trying to handle him everyday, giving him treats to try and make him more trusting, i think the best option is to get him neutered. It would be much appreciated if some more experienced rat owners could give me some advice on my situation. I would like him to be tame but if it’s common and it’s just in his nature that he doesn’t want to be handled then I will accept that but i want to try everything before he’s just in his cage and hour run with no interaction. Thanks