Darcy is looking for this one!
She asks:
I need help finding a book. I’m pretty sure it was a part of a mafia series.
This particular book the main male character suffers from blackouts because childhood trauma where his sister and he were tortured because of a genetic condition that makes them less susceptible to pain. His sister dies and he’s haunted by her memory (she’s not a ghost, just a hallucination).
Her brother keeps her at a convent to keep her safe and that’s where he meets her (I’m pretty sure anyway).