Joe Jonas is reportedly dating his brother's ex-girlfriend.

The 25-year-old singer has been spending a lot of time with 19-year-old Gigi Hadid, a model who Nick Jonas, 22m romanced before embarking on a relationship with Olivia Culpo.

A source told RadarOnline.com: ''Joe and Gigi have hung out a few times this week actually.

''They have visited a museum together and even went to the park together on Thursday.

''Nick and Gigi [had] an ongoing thing. The fact that Joe and Gigi are hanging out now is just strange.''

And Joe's ex-girlfriend Blanda Eggenschwiler is said to be furious about his new romance as she is friends with Gigi.

The source said: ''Blanda is absolutely furious.''

Blanda is said to have told friends: ''Nick and Gigi dated several times in 2012 and 2013.''

Joe and Blanda split up last month but it was claimed earlier this month that the singer was feeling ''torn'' about the break-up.

A source said: ''On the one hand, he cannot stand her. And on the other hand, he is still in love with her.''

And it was claimed Joe had been relying on Nick and older brother Kevin, along with close friends, to get him through the split.

The source added: ''We are all totally there for him. He is doing so much better without her and we're just happy she is gone. Joe is such a sweetheart and it is just good to have him back and present.''