My perspective on this is as follows: I was once engaged to a woman who had a small child. This engagement lasted for over two years, and over that time I grew to genuinely love both of them. (By the definition I gave above.)
Why was my engagement stretched out for so long? Because while she had fallen away from her church and was professing atheism, I sensed that that was a temporary condition. And one day she informed me that she had found faith again, and when I didn’t immediately renounce my atheism she declared that I was Satan himself and dumped me on the spot.
This is not intended to be a sob story. Why not? Because in the time since then my love or both her and her kid has faded away. I worried about how they were doing for a while, but I don’t anymore. I had no contact with them and over the years it faded away. I don’t wish them ill or anything, but I’m not at all concerned about them either.
So love can come and go. Can a parent’s love come and go? Interesting question. My take on it is that parental love is the same type of emotion I felt; they’re just (usually) given a massive infusion of it when they meet the kid. And if the emotion functions the same way then it would indeed be possible for it to erode away to nothing given the right circumstances - though it’s also possible that the massive infusion of it that they started with is too large to be whittled away in a lifetime.