Things are heating up between an unlikely couple, top fashion photographer Terry Richardson and Audrey Gelman, the press secretary for Manhattan Borough President Scott Stringer, according to sources. The hipster lensman, 46, and the budding politico, 23, just returned from a Mexican vacation together, and Richardson posted shots of Gelman posing in the surf and sand on his TerrysDiary blog, with cutesy captions like, “Me and Audrey in Tulum,” “Audrey watching the sunset” and “Audrey in the Caribbean Sea.” Richardson’s blog also routinely features shots of street art, celebs and the many models who visit his studio, including Georgia May Jagger, Karlie Kloss and Kate Moss. Richardson also posted images from his birthday at the Carnegie Deli last week, with Gelman by his side as he blew out his candles. “He is so happy,” a source said of Richardson. “He’s completely into her. He’s even talking about having babies together.” A rep for Richardson, and Gelman, had no comment.