Should a relative of ours file for paternity/retain a lawyer? & file for harassment?

Hi, we have 2 problems. Basically, our close relative, who is himself single (divorced), slept with a woman who was separated from her husband at the time, & she became pregnant with his child. She then went back to her husband & tried to act like it was his. then after she had the baby she conceded it was not his, our relative filed paternity, then retracted when she said she'd work out of court. but she hasn't, & has tried to extort, blackmail & threaten in order to get her way & has withheld his child from him. she has also threatened him & our family various times & is constantly sending degrading & nasty texts unsolicited. Should he refile for paternity asap if she won't work with him amicably outside of court? Should he file harassment charges? should the rest of our family file harassment charges?