Taylor Swift and Selena Gomez
Courtesy of Taylor Swift
07/23/2013 AT 08:00 PM EDT
They don't look anything like sisters, but Taylor Swift
says they could be.
The singer Tweeted a cute picture of herself
and Selena Gomez
on Monday, with both stars perched upon a balcony above the sea while striking a pose to imitate the mermaid sculpture between them.
"Happy 21st birthday
to my friend, and the closest thing I've ever had to a sister, @selenagomez!!" Swift Tweeted.
The pair have been friends for roughly five years, and seem to be very supportive of one another
. They often say sweet things about each other:
"I met [Swift] when she was 18. This is before [Swift's 2008 album] Fearless
came out, and it was absolutely incredible to see someone so successful and so humble," she says. "I think she has been a big part of me kind of staying the way I am too," Gomez has said in the past