Rory Kennedy and Taylor Swift. 

PARK CITY, Utah - Rory Kennedy and Taylor Swift: They've been quite the odd couple at Sundance, where the country/pop singer somewhat inexplicably showed up to the red carpet premiere of Kennedy's HBO documentary about her mother, "Ethel." On Sunday, Kennedy opened up about their budding friendship, telling ABC News Now's "Popcorn with Peter Travers" that she and the 22-year-old Swift are so close that Swift has written a song about the iconic American family.

"She really just loves my mother which is so sweet," Kennedy said. "I'm a huge fan of hers, I have young girls and we had been to a few of her concerts. I met with her at one of them and she had read a ton of books about our family. She was inspired and wrote a song."

After that, Kennedy extended an invitation for Swift to come to the Sundance premiere of "Ethel," and on Friday, there she was. Kennedy also said that while the family's a fan of Swift, they themselves are not so musically inclined. "My uncle Teddy, he had a good voice," she said. "We are actually terrible, terrible singers but we love to sing."