NC for this, as I totally get you, OP. My parents were in many respects very loving - middle class, stately homes visits, the lot. They had a terrible, mutually abusive marriage, though, and it poisoned both of their personalities and was spread around the family and my siblings until we all were contaminated by it. They played my siblings and I off against each other, so that even now huge family fights break out with one sibling being absolutely vile to another, and despite any veneer of cordiality we all know we don't like each other really :( I don't love my siblings. Which is awful. I wish we had a proper bond.
Now I can see exactly what my parents did in creating favourites, using each of us to score points, taking out their frustrations and inadequacies on us, and so on. It was a very shouty house where even in an apparently calm period a screaming row could erupt out of nowhere. My dad is cold and often verbally abusive, and my mum, who was very loving and easy-going when we were little, sort of became like him, and when we were adolescents she started to treat us as if we were versions of him. They were both often emotionally abusive to us in small ways - my dad specialises in apparently minor but curiously cold and hurtful below-the-belt comments; my mum likes to blow up and say horrible, really horrible, things, then pretend those didn't matter because it was all just in temper. But anyone who has ever lived like this (and I bet on this thread, lots of people have!) knows that if you live a life where people randomly blow up in temper and behave abusively and appallingly, then everyone has to pretend that everything's nice and normal for the rest of the time, it is incredibly, incredibly emotionally damaging.
As a young adult I began to keep my distance because they were so emotionally confusing and hurtful to be around, so I carefully rationed the time I saw them, but I think I still loved them. I still believed that they would do anything for me if I ever needed it. It was only when I had a family myself and was very emotionally vulnerable that I really needed them - I had a traumatic birth and a lot of other awful things happened to me around the same time, I was a mess and really in need of help and love. And they not only let me down, but my dad in particular was totally vile to me in a way that would make you gasp if I told you all. I have never quite recovered, because I realised that not only were they not there for me, but they had the capacity to actually hurt me when I needed help. I don't know if they were always like that, or if they grew to be like that, but at some point after that I realised after that that I didn't love them any more. Just felt detached and sad, like other posters on this thread have said. (It's a wider issue, though, for me, as since then I feel emotionally numb about everything to be honest, I don't know if my sense of love will ever really come back.)
I don't know if I will ever love them again. My dad in particular has just behaved so badly towards me in the last few years that it would be hard to love him again, because he's so readily demonstrated that he doesn't really love me; or rather, that his love for me is totally overwhelmed by his own love for himself and his own ego issues. An object lesson in how you can't expect to treat your children horribly and then be surprised if they don't love you any more. I can't help it, there it is.
I do worry that I am going to become like them, especially when I am irritable with my DC. I don't want to be hard to love :(