I fail to see how it was incest. It's not like they're blood-related

Incest is when people of the same family have romantic or sexual affairs. Not everyone in a family is really blood related even if biological but it's still incest. Biological family, adopted family, found family all count as incest and it's weird even if it wasn't. Imagine growing up to loving a toddler you watched grow up and who called you "mom".