Two Cats brother and sister are having issues

Hi im a new cat owner, Actually I own 2 new cats, they are brother and sister that are a year old.When I adopted them, I was able to take the boy home, but not the girl because he was fixed, and she wasn't. When I brought the girl home the next day after she got fixed, the boy started to act funny around her. He began to start biting the back of her neck, and I mean grab on it and not let go. She didn't seem to mind too much, but it would last for 3-5 min at a time, with her finally kicking him off of her. Is this a sibling thing or is this a behavior problem that needs to be worked on. They don't seem aggressive towards each other, its just he does that to her over and over again. Its not like they are strangers to each other, they have been in the same cage together in the shelter, and they are familly.

The behavior you described is not unusual. It is the way that one cat expresses dominance over another. He was simply saying "don't forget, I'm the boss!"

It is also how a male will mate with a female. If he was neutered less than 3 weeks ago, it is possible that he still has enough testosterone in his system that he is still able to feel a bit lusty around females. If it is his libido rather than dominance, this behavior will likely disappear soon.

Hi! I see it has been a while since you posted this, so I hope this isn't too late My 2 cats are bro and sis as well, and he acted the same way when he got fixed. I brought them both home from the vet at the same time, and he kept trying to mate with her! My vet said it would take a while for his hormones to settle down, and sure enough they did, much to his sister's approval!!! Good luck.