Has any Champions ever fought their stablemates for the Title?

It happens all the time. PBC, Top Rank, and DKP have done a lot of this.

 

I'm not quite sure what you're asking. The title of the thread doesn't really match your first couple sentences.

Boxers can be in the same "stable" of a promoter or a trainer, but they can have different managers.

I believe Carl King was the manager of record of both fighters when Tim Witherspoon and Bonecrusher Smith fought for the WBA Heavyweight title. But they weren't in the same "stable" and didn't have the same trainers.

Lamon Brewster and Kali Meehan were quite close and routinely trained together before they fought, and Meehan helped Brewster get ready for his first fight with Wlad Klitschko. Then Brewster made his first defense against Meehan. But they weren't managed by the same guys.

Ali and Jimmy Ellis fought in a non-title fight in 1971. Ellis and Ali were stablemates. Angelo Dundee trained both but he was also Jimmy's manager. When they fought, Dundee worked Jimmy's corner, so he could get paid as a trainer and a manager.

Stuff like that.

 

Secretariat VS Riva Ridge, I 'spect.

 

I immediately thought of Zarate and Zamora but that was fought as a non-title.

 

Not exactly what OP is talking about, but still maybe the best example of two close guys fighting:

Simon Brown and Maurice Blocker were stablemates on the way up in Washington DC and sparred regularly for years. They were best friends.

Brown won the IBF welterweight title. Blocker won the WBC.

Brown signed with Don King. Blocker signed with Butch Lewis, breaking up their stablemate relationship but not their friendship.

They fought to unify, with Brown winning by TKO in 10.

https://www.upi.com/Archives/1991/03/17/Brown-Blocker-friends-who-hit-each-other/4537669186000/

 

Danny Jacobs vs Derevyanchenko.