Jesse Williams didn't violate a custody order by letting his kids hang out with a woman his kids call "Mama C" ... because she's not his girlfriend, according to sources close to Jesse.
We broke the story ... Williams' ex, Aryn Drake-Lee, claims he violated their custody agreement by introducing their 2 kids to his new gf ... Ciarra Pardo ... well, at least Aryn thinks she's a gf.
According to our sources ... Jesse and Ciarra, a visual artist, have known each other for a very long time, but are not a couple and don't ever hook up. In fact, we're told Ciarra's been a pal since the kids were born, and Aryn knows her.
The two were recently on a trip together, joined by other friends, to Brazil.
As we reported, Aryn says the kids call Pardo "Mama C" and claims Jesse's been taking them to her place since October. Our sources say the kids have always called Ciarra "Mama C" and also "Auntie C."