AFAIK, only the primary JPMR cardmember gets complimentary Unted Club membership. But the primary can bring in either immediate family or two guests with his/her United Club access.
https://www.united.com/web/en-US/con...ge/access.aspx
It would be kind of insane if they offered JPMR AUs full UC membership. Pay a $75 AU fee and get a $550 lounge membership... yeah, people would abuse that.