Aaron was actually surprised about how good he was with them. Aaron never had kids and made sure to keep it that way. He knew how to play it safe - how to use protection with girls he knew less than a day if and when he decided to take them to his bed for an easy "stress reliever" as he liked to call it. He didn't leave any connections; no ties that could be traced back to him. He wasn't the kind of guy who made mistakes like that.
"I guess I just love kids." Whether that just concluded in Aaron being a great father someday, it just seemed likely to be brushed off later on in his life. He didn't have any room for a family or if he wanted to corrected himself he just didn't have the time.
Again, it seemed that he never did stuff he wanted for himself.