AceShowbiz -

Nicole Richie is worried about her little sister Sofia Richie who is currently dating Justin Bieber. The former "Simple Life" star fears the "Cold Water" hitmaker will get Sofia pregnant.

A source tells the National Enquirer, "Nicole is freaking out! She's worried Sofia will wind up pregnant and alone." According to the outlet, Sofia already experienced a pregnancy scare as "she'd taken a home pregnancy test that came back positive, [but then] took two more and both were negative." The source adds that Nicole is "worried Sofia's on a collision course with disaster."

Another insider previously told Radar Online that Nicole's fuming after knowing Sofia's relationship with Justin. "Nicole is flipping out right now over the fact that her sister Sofia is dating Justin Bieber!" the insider revealed, "Nicole told Sofia that she is just setting herself up for disaster and it has caused a huge rift between the two sisters. Sofia told Nicole to just mind her own business."

"Sofia also told Nicole that she and Justin are for real," the insider added, "But Nicole thinks she knows how this will end and she is only trying to protect Sofia from getting hurt. Sofia is not going to listen to anything that anyone has to say - not even her own family members. She is set on making Justin her boyfriend."

While Nicole hasn't commented on the report yet, another source close to the situation tells Gossip Cop that it's "ridiculous" and "untrue."