Thesis Frankfurt is right that we don’t love our children for their qualities, and all love works that way
Where it stands
I left accountancy to raise two children, so I have had a lot of time with the evidence.
Harry Frankfurt argues in The Reasons of Love that love is not a response to the beloved's value. It is a form of caring, and caring is what makes the beloved important to us. His model case is a parent's love for a small child, which he treats as the purest kind. A parent does not love a baby because it is exceptional. It mostly isn't. The loving comes first, and the child matters because of it.
I want to go further than people usually do and say this is the model for all love, including friendship and romantic love. Here's why. Every attempt to ground love in qualities runs into the problem that qualities are shareable and love isn't. Every attempt to ground it in the shared history (Kolodny's view) makes it hard to explain love at the beginning of a relationship, before there is any history. Bestowal explains both: love is something we do, not something the beloved earns.
It also explains why love can survive the loss of the very qualities that started it, which every carer of someone with dementia knows.
So my thesis: love is bestowal, all the way down. The qualities are where it often starts, not what it is.