You really should talk to your parents about getting him neutered. First off you really shouldn't think about getting another cat until you get him fixed. Expecially if you let him outside to roam. Once he gets a little older he's going to start roaming (finding a girlfriend). He may not come home. There are so many unwanted pets out there that by not neutering him you are adding to the pet overpopulation problem. He may also become aggresive and when you do bring him inside he will mark his territory (pee on your stuff). He's still young, so you want to take him in as soon as possible to get neutered.