First post...let's see,I joined this site to ask some outer sources for advice!

Might as well get to the point I guess,

My boyfriend and I recently started working with two horses that belong to a family friend.

He's riding a 9?y/o APHA mare,quiet disposition, and I'm riding a 7?y/o Arabian gelding. He's high-strung, but no where near impossible.

Neither have been ridden in over a year, but in our previous rides in the past few weeks, both are doing pretty well.

My arab,however,has a bad case of seperation anxiety when I take him anywhere away from the paint mare,when the mare is ridden to another paddock or around the block and out of sight.The arab loses all interest in anything but her and becomes unruly-biting,kicking,head tossing,etc.I have been longing him in a round pen when she is ridden away,as well as riding him in the opposite direction,but other than that, I need some help!They have been together for nearly 10 years,with minimal interference.I understand this typical, and who knows, maybe the solution is simple and I'm the only person that can't figure it out!He's a good mount,just a little rusty here and there, but nothing that can't be fixed with a little work.How do I break this horses complete flip in personality when seperated????