They have a daughter named Mia Love.
Rubin and the 20 year-old lady started their love affair in November, shortly after his marriage to Paula Patton fell apart.
Despite his parents' disapproval with the speed he's taking with Geary, "he doesn't want to risk losing her."
"Both his parents have told him to take some time and not rush into marriage again so soon," the source added.
But the "Love After War" singer doesn't care what the naysayers think and is reportedly head over heels in love with Geary.
Note: not confirmed