After a brief separation earlier this year, the "Roar" songstress and the "Paper Doll" singer rekindled their hot romance. They "realize they must be together," a pal said of the couple, who released a sweet duet, "Who You Love," in August. In fact, sources say the pair may be headed for marriage. "He's just a fantastic partner," Perry gushed of her boyfriend in Marie Claire. "It's a rad, mature relationship."