geldings getting along

[RhndLev@cs.com]

This isn't exactly endurance related, but I was hoping someone on the list 
could help me with a question about my two geldings fighting.  My Appy 
gelding is turning two this year.  I've raised this horse from a baby and he 
has been the sweetest, most mellow horse to deal with until about a couple of 
months ago.  A couple of months ago, he started developing a real attitude -- 
at about the time that Special came to live with us and my Arab filly came 
home after the show season -- whether that is coincidence or not, I don't 
know.  Anyway, since that time, he has challenged me (kicked me) and keeps 
challenging my old TWH gelding, Laddie.  And I'm not talking about just 
biting at each other -- he's lashing out with front hooves, kicking with both 
back legs, running from one side of an 80 pasture to the other just to kick 
at Laddie, etc.  So far, Laddie is holding his own, but he is getting up 
there in years and has a history of hock problems and I'm getting really 
concerned about him getting hurt.  The Appy is already about two inches 
taller than Laddie and almost as heavy, and he's still growing.

So, can anyone tell me if this problem is a big concern?  Or should I just 
sit back and wait for the Appy to outgrow it?  How long does out growing it 
take?

Rhonda and Special