BRAD PITT I WANT JOINT CUSTODY OF OUR KIDS Divorce War Brewing

Brad Pitt has just set the stage for a custody war ... asking for joint custody of the 6 kids he shares with Angelina Jolie ... TMZ has learned. 

Brad answered Angelina's divorce petition and squarely takes issue with her request for sole physical custody of the kids. She wanted Brad to only have visitation.

TMZ broke the story, Angelina checked the box for sole custody after Brad allegedly struck Maddox on a private jet.

FYI ... California judges favor joint custody, unless it would be harmful to the kids.

Neither Brad nor Angelina mention spousal or child support.

Brad gives the same separation date as Angelina ... Sept. 15th.