He's 7 months. You can geld them as soon as they're born, but if you don't everything goes back up, and its best to wait until they drop again to do it, which should be in the next few months. Doing it now, while they're not dropped, although possible, it's risky. Waiting until he drops, will be much safer, and it will probably be around a year of age, it is very unlikely that he will keep a stud "attitude" if he's gelded as a yearling or a little sooner. I'll be keeping an eye on him so I can take him in as soon as he drops, that way he doesn't breed June.
As for your gelding, he may have been gelded at 2 years, or after he bred a mare, which would be a cause for the attitude, but I firmly believe you can train the "stud attitude" out of them.
Also as a rule of thumb, however many years old your horse is is how many months it should take them to start acting like a gelding. I doubt that's a proven fact or anything but it does work out like that for a lot of people.
Me and my cousin went on a trail ride yesterday, me on June and her on her stud horse, and they were both so quiet you'd think we were riding two geldings. She got him as an unhandled 6 year in February, and she works hard with him everyday and that's how he is now.