(This is an What if Scenario, don't take it seriously. Like What If Lucifer and Sera were in love and Emily is Lucifer's dauther)

Lucifer, having once been in a relationship with Sera before the fall, left behind a family he didn't know he had when he fell as Emily was born afterwards.

Sera, still bitter about it, is partially wondering if she wants her secret daughter to be her weapon against Lucifer, but can't bring herself to do so, as Emily has her father's joy.