The Instagram photo shows Turner, 23, on a tree-lined street, facing away from the camera with her arms out, adding more fuel to the fire that she could be expecting.
Jonas, 30, captioned the snap simply with a black heart.
Multiple outlets reported on Wednesday that the rocker and the “Game of Thrones” actress, who wed in 2019, were expecting a baby, although the stars have not confirmed anything. At the time, reps for Jonas and Turner both declined to comment on the speculation.
Turner and Jonas began dating in 2016 and tied the knot in a surprise Las Vegas ceremony in May 2019. They held a second, more formal ceremony in France over the summer.
Joe’s brother Kevin, 32, and his wife Danielle, 33, have two children together. His other brother Nick, 27, and his wife Priyanka Chopra, 37, wed in 2018.