Idris realized he was falling in love with Ila when she was mid-to-late teens. He understood the gravity of those feelings, though, and didn't let them affect his judgement as her parent or how he behaved around her--the very last thing he ever wants is to hurt her, and for a long time he's convinced that those feelings, if she ever knew about them or he ever acted on them, would hurt her. So he pretty comfortable just, doesn't acknowledge those feelings for many years and things are business as usual.

Ila recognizes that she has some kind of attraction to Idris around this same time period, but it doesn't blossom into a full awareness of her own feelings until after she's away at an out-of-state college and she realizes just how much she misses him. Which results in her writing and self-publishing incest fiction. Which turns into her getting harassed off-campus when she gets doxxed by a couple of determined shitheels, whiiiich sets the stage for the car accident that is the catalyst for the novel in the metal band setting.