What do I do when all my boyfriends children's mother does is harass me and take the kids away from him because of me?>?

You stay out of the drama. This is your bf's issue to settle with his ex. The other woman is using whatever and whoever she can to get to your boyfriend.

He is the one that needs to take care of the visitation arrangements. If he needs to go back to family court, then so be it. Were they married? Is there any document showing the vistation and shared custody?

As angry as you might get, it is not worth it for you to jump in with fury and stir the pot here. This is already a volatile situation, you do not need to add to it. Tell you boyfriend about how you feel and then let HIM take care of this.

You do nothing, take care of your own. Baby mama drama come with the territory, when a guy has a lot of babies all over the place.

Next time pick your partner wisely, lots of women I know don't date men who have already had kids.
It's not fair for the men, I know, but hey, you have choice, do you?

You be there for him. They are little lonely leaches, maggots, ticks (get it) that has an objective to drive him nuts. You just stay out of it and help him mentally, emotionally, just don't get involved. POLICE LOCK PEOPLE UP THESE DAYS DEALING WITH SITUATIONS LIKE THAT. I hope he got a DNA test for those kids, they might not even be his and they are making his life miserable. Good luck

It's none of your business. They have to work it out. If people are going to use excuses to play with each other they will find them be it you or something else. Just step back and let them try to work it out.