Hello there. My family just got a new cat a few months ago named Jenks. He is male and about a year old. He has been extremely aggressive towards our senior female cat named Peanut. It seems that Jenks has wanted to mate with her, so we got him fixed. He is still chasing her though, and I am afraid for Peanut's all over well being since it seems to be getting worse - help!

Can you describe their behavior in a bit more detail?

They may be fighting for dominance. It's also possible that they simply do not get along. Not all cats can live with other cats, and some personalities just clash.