What does it mean if a guy likes all of my pictures on Instagram?

We have known eachother for a long time and he has a girlfriend and a baby. He literally likes every single one of my selfies on insta but not on Facebook bc his girlfriend has fb and not insta.

He usually doesn't talk to me (his girlfriend hates me and he knows it.)

Is he flirting?
What does it mean if a guy likes all of my pictures on Instagram?
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