I'm not sure I believe that parents love their children, for instance. My father was loaded with rage and wrapped up in himself and didn't pay much attention to my mother. After I was born she used me to fill the emptiness niche in herself by basking in attention from me.
I strongly believe that the reason she accepted me after transition was because I was the only source of "love" in her life. On several occasions she's complained that she wished I would say that I "love" her.
However since she's frequently been extremely manipulative I don't trust her and as such only feel a sense of duty toward her. (Perhaps the best example is while in the hospital recovering (or perhaps before, I don't quite remember), she told me that she had thought of threatening to commit suicide if I were to go through with surgery, but she didn't think that would have stopped me so didn't bother. It was recently pointed out to me that there was an extra "you don't care about me" message to add an additional level to the manipulation.)
The frightening thing is I suspect that my two intense relationships I was probably trying to use them to try and help me feel good about myself.
I am left with the conclusion that I've never experienced any form of love other than whatever form might exist in friendship.
A corollary might be why do I want a romantic relationship, never having experienced a functional one? Where did I get the idea? Is it entirely motivated by looking for an external source of acceptance?
(And most importantly is there anyway of getting me to stop wanting one? It would be quite helpful for me to stop becoming depressed upon being reminded about other people's romances.)