Brody

Question
I have had Brody for over 5 years and he is a male mini rex with an exceptional temperment.  I have noticed that he is exihbiting aggresive behavior with our rat terrior (girl), children (boys) and our tabby cat(male) with whom he has known since birth he has also started nipping at our ankles while in the back yard.  He is most comfortable with our cat but seems very agitated with Roxy our girl dog. He is chasing us more also... Is this normal? Or is there something we can do?  He answers to his name and usually interacts with us and our other pets fine..? Just Courious, and spoiled with a very fine bunny!

Answer
There are two questions that pop in my mind.

First, is he intact?
Second, has something in the household changed?  Any visitors in terms of people or animals?

The nipping and chasing makes me wonder, if he's intact, if something hasn't finally triggered his hormonal response to mate.  Does he circle in any of his chases, or does he just chase?  Circling, is a sexual thing, that's why I ask.

If he is neutered, has something new happened?  A visitor, any kind of change in the house like moving stuff around, remodeling?  Even a new perfume or cologne could trigger something.

The other thing is, are there any signs of changes in his health?  Drinking more, changes in eating?  If he's feeling under the weather, he could be more grumpy, but I would expect that to be seen when he interacts with everyone.

What you describe makes me think of sexual behavior, but this is often seen first at an earlier age.  

Sorry it's not an exact answer, but if he is neutered, you may have to do some detective work to think back if there was any thing that may have triggered his behavior changes.