. . . Joe Jonas!
OK, this one is a doozy: Taylor and Joe dated briefly in 2008 (he reportedly dumped her over the phone, and true to form, she wrote a song about it). Joe began dating Demi Lovato in March 2010, but they split a few months later. In Summer 2010, he and Ashley started a relationship; they broke up in May 2011, and in November, Ashley spoke about Demi's personal troubles, saying, "I'm really happy that she's doing well," adding, "She and I never had a problem with each other, but you know, it doesn't go away. Jen Aniston still gets asked about Angelina Jolie."
In June 2015, Joe began romancing Gigi Hadid, who is one of Taylor's recent pals. Gigi starred in Taylor's "Bad Blood" music video and has been spotted on multiple outings with her, including a group lunch with Joe. Taylor admitted her friends' overlapping relationships in a Vanity Fair interview when talking about how the group stays drama-free, saying, "We even have girls in our group who have dated the same people. It's almost like the sisterhood has such a higher place on the list of priorities for us. It's so much more important than some guy that it didn't work out with."