On the show to promote her new single, "Heart Attack," the 20-year-old Lovato said she spoke to her sister for the first time when she turned 20 last August.
"I thought that was so incredible," she said. "So I actually have three sisters, that I didn't know until this year."
I asked her, 'Why haven't you ever contacted me? And she just said, 'Well, because I never wanted you to think I wanted anything from you. So I've just kind of been waiting to see if you wanted a relationship,' and I just thought that was so incredible.
Lovato has two other sisters, Dallas Lovato and Madison De La Garza.
Police: Sword-wielding man demanded free tacos
Puzzle-maker slips 'Murdoch Is Evil' into Rupert Murdoch's Sunday Telegraph