Based on your version this guy seems like a real bum. Family is a lot more than DNA. If he isn’t willing to accept his responsibilities then he is nothing more than a sperm donor. If he doesn’t care the rest of his family probably won’t either. However he is obligated to help support his child, and I would hold him to that. If you press for the courts for paternity tests his family will learn about this anyway. For now I would lower the temperature and don’t give out any unsolicited information. Brining others into this may only escalate tensions.