If biological dad has almost four yrs of inconsistent child support and hasn't seen the kids in over two months can I as biological mom file abandonment charges and have his rights terminated? He has never provided healthcare for the twins either

Nope.

What do you think doing so will get you? Please review this:

https://www.askmehelpdesk.com/family...st-364259.html

No, all you can do is take him back to court to try and perhaps garnish his pay.
Merely missing payments and not visiting is not enough to take rights away