Jennifer Lopez Takes Ben Affleck's Son Samuel to Lunch

Jennifer Lopez and Ben Affleck aren't getting "On The Floor" together anymore ... but, she's clearly a committed ex-stepmom -- 'cause she took his son to lunch!

The singer-songwriter took her child Emme to lunch on Saturday ... and, she stunned in a white crop top which showed off her ripped abs.

She added a pair of low-rise black pants to the ensemble as she walked with Emme and Samuel, Ben's 13-year-old son.

Check out the pics ... Samuel looks a little like his dad in a t-shirt and some pale shorts as he follows behind J Lo.

No Ben on this outing ... just Samuel hanging out with his former stepmom and stepsibling -- which makes sense when you consider how close the families are when they were linked by marital bonds.

We've told you all about Bennifer's marriage which came to a close earlier this year when they settled their divorce ... but, he exes have worked hard to stay in lives of their children.

They attended a back-to-school event together, went to lunch as a group and have generally tried to keep things civil so their kids can have a relationship.

BTW ... seems like a busy weekend for Samuel -- who went out with his dad, his mom Jennifer Garner and his paternal grandmother in Los Angeles Friday night.