El DeBarge was right ... his famous incarcerated brother James DeBarge has finally settled his MJ beef with his fellow inmate Conrad Murray ... and all it took was an honest jail house conversation.

TMZ broke the story ... James -- Janet Jackson's ex-husband -- held a serious grudge with Murray because he blamed the doc for killing his friend Michael Jackson.

But now we've learned ... the two managed to have a confrontation behind bars at the Men's Central Jail facility in L.A. in the past few days ... and "squashed the beef."

TMZ spoke with James' wife ... who says the singer was very impressed with Murray and that James "has made peace with what happened to Michael."

We're told James no longer believes Murray is an "evil" man or a murderer ... instead he told his wife Conrad is a "kind man."

So, we gotta ask ...

El Debarge says his famous incarcerated brother has a serious beef with jailmate Conrad Murray ... but El is confident the two can eventually work things out ... if Conrad plays his cards right.

As TMZ first reported, James and Murray are both being housed in the Administrative Segregation of the L.A. County Men's Jail ... which is awkward since James was Michael Jackson's brother-in-law back when he was married to Janet Jackson in 1984.

El -- who was leaving Tru nightclub in Hollywood last night -- told us his brother is a very loving man ... but insists James was pissed at Murray over the circumstances regarding MJ's death.

El tells us, "I don't really think they've had a chance to do a one-on-one talk and get an understanding ... I think once they finally do that, it'll be OK."

Still, El warns Conrad that forgiveness won't come easy ... "My brother James, he ain't no joke. My momma didn't raise no punk."

Look for El at the Grammys on Sunday because apparently he still makes music and was actually nominated.

There are nearly 4,000 inmates at L.A. County Men's Jail, so imagine the coincidence that Dr. Conrad Murray is in a cell just feet away from Michael Jackson's former brother-in-law.

James DeBarge -- Janet Jackson's ex-husband -- is locked up after being arrested for assault with a deadly weapon and drug charges. DeBarge -- who was the lead singer of the wildly popular band, DeBarge -- has been placed in Administrative Segregation -- the place where famous inmates with security issues are housed.

Murray has been calling the Ad Segregation unit home since his conviction on manslaughter charges last November.

We're told they occasionally run into each other, most recently last Monday when they were each meeting with their respective lawyers in the visiting room.

DeBarge's lawyer, Spencer Vodnoy, tells TMZ ... the singer is "really upset" he's so close to Murray. DeBarge says even though he was married to Janet for less than a year back in '84, he thought of Michael as a brother.