It sounds as if he acted as her father and the relationship was recognised as a parental one on both sides, similar to adoption. Therefore it would be a kindness to acknowledge it without showing a cold clinical "non-biological" at the top of the profile. It's possible to give a sensitive description in the biography. If you're not up for that, omit it. (I'm not saying the status can't be marked as non-biological on the edit tab, just that it shouldn't tactlessly be trumpeted on the display tab.)
I'm not sure why my vote is so heavily challenged here. People voting "yes" weren't even asked to give reasons, and only Edison has done so. That doesn't seem very symmetrical. Anyhow, I've made my point.