nahh
I don't think so, if i read it clearly, they are most likely a sibling
she probably took her dead sibling's name as a stage name
kinda insane thinking abt it but like okay sis
main character has memories of a past life.
mom looks just like the idol (who was banging on the car door)
most likely he was her brother that passed after an accident of smth.
it would also explain his timid & small stature as a soul (when being chosen to be a doppel. because he was literally a younger soul when he passed)
they probably share a last name that he cant remember but his brain is telling him its Seong
Ohhh yeaa kinda make sense, why I didn't think he might have siblings
Don't tell me...
Seong-ah (the girl idol one) used to be the doppelganger who killed our seong-ah??