When the long-running ABC series "Grey's Anatomy" season 12 returns in February 2016, viewers can expect to learn what Nathan's (Martin Henderson) secret connection to Owen's (Kevin McKidd) sister is.

During the midseason finale, Owen confessed to Meredith (Ellen Pompeo) why he hated the new doctor in Grey Sloan Memorial Hospital. Even though the details were not revealed, it appeared to revolve around the redhead's sister. Owen certainly talked as if she was dead and that Nathan was the reason why. What stumped the fans was seeing how Owen's mother maintained a good relationship with Nathan. She visited her son in the hospital and was surprised to find the other man there. She even hugged him, while he called her mother.

CarterMatt posits several reasons why Owen could not stand being in the same room as Nathan. According to the website, it is possible that he and the sister were involved romantically and it ended badly. He could have cheated on her or she just died. Owen holds Nathan responsible for what happened to her, perhaps because the latter failed to save her. Another probable cause of the hatred is that Nathan used her for his own benefit. He might have stepped on her to get to where he is right now and somehow, Owen's mother does not know about his betrayal.

Meanwhile, creator Shonda Rhimes told Entertainment Weekly that the second half of the series would be revolving around Meredith. She said that it would explore where her main character is going and who she is becoming. She also said that the midseason premiere would not be as harrowing as the last finale.

"We've been having a blast. The first episode that comes back is extraordinary and very, very powerful, and directed by Denzel Washington. It certainly puts us on a path for the beginning of the second half of the season," she shared.

"Grey's Anatomy" season 12 will return on Feb. 11, 2016 at 8 p.m. EST on ABC.