Kate Hudson’s romance with Alex Rodriguez is more than just a fling. “It’s somewhat serious,” a source tells People. “He introduced her to a bunch of his friends.” Kate also followed A-Rod to Dallas last month, with son Ryder in tow, for the Yankees' series against the Rangers, and they “worked out together in the fitness center,” says a spy. But will it last? “You never know with Kate,” another source says. (More Kate Hudson stories.)