US songstress Demi Lovato has revealed she has an older sister she's "never known [her] whole life".

During a radio interview with WBLI’s Dana & Jeffrey Show the star explained that she's only recently found out about her sibling.

She explained: “I have an older sister that I’ve never known my whole life. She’s in her 30s. She’s my half-sister but I talked to her for the very first time in my life around when I turned 20. I asked her, I said ‘Why haven’t you ever contacted me?’ and she just said ‘Well because I never wanted you think that I wanted anything from you… I’ve just been kind of waiting to see if you wanted a relationship.’”

Lovato - who also has sisters 25-year-old Dallas Lovato and 11-year-old Madison De La Garza - is estranged from her father.

The 20-year-old songstress is looking forward to getting to know her new-found sibling over the coming years.

She added: “I just thought that was so incredible… I have a third sister that I didn’t know until this year.”