I was born as a result of a shortlived (extramarital?) relationship. My parents never lived together but my dad showed up to visit me 2-3 times a year throughout my childhood. He was quite flaky about this and I realise in retrospect that eventually my mum stopped telling me in advance if he was coming to see me, she waited for him to actually turn up. He was sometimes fun but he didn't feel like a proper dad, there was no familial intimacy, he was just this bloke who sometimes turned up and occasionally took me to expensive shops and let me choose toys or clothes.
The thing I remember finding difficult in childhood was being able to explain where he was - I remember primary school friends asking me whether my parents were divorced, and not really knowing how to answer.
By the time I was a teenager most of my friends seemed to live in single parent households and I didn't confront that need to explain any more. Plus I suppose teenagers are much more oriented towards friendships than family relationships, or at least i certainly was. He paid my mobile phone bill and we stayed in touch slightly more via text, but there was still no 'real dad' closeness. Overall his relative absence didn't bother me at this age.
As a young adult (and ever since, really) I've been less in contact with him. Life is busy and when I do see him, I feel that I'm expected to do the emotional work and the good manners (I politely listen while he talks about himself). Objectively I can see he is a kind-hearted, generous, self-absorbed, thoughtless man, who isn't really cut out to be a father and presumably did not really want to be one.
My first serious relationship was really unhealthy - I committed much too quickly to someone (much older) with whom I was not really compatible. It was quite a controlling relationship in both directions, and it took me much too long to leave it. Since then (15 years ago!) I've kept my relationships quite short, always with one foot out the door, quick to cut my losses. I'm not sure whether my first awful relationship was a response to fatherlessness, or whether it was about my mother's emotionally distant 'love', or whether it was entirely coincidental; and I'm not sure whether my subsequent expendable relationships are about fatherlessness, emotionally distant mothering, or simply explained by that first relationship where I accepted too much and stayed too long.
I had my own children via sperm donation. In some ways that was about comfort with a single mother setup and feeling confident replicating it, in some ways it was i suppose about having a family in a format I understood (and I think that's defensible - plenty of parents in nuclear families are doing much the same sort of mindless reproduction of their own parents' arrangements), and certainly in some ways it was about being aware that parents other than the birth mother can and do disappear, flake out, not show up when they say they will, and wanting to protect my children from that.
I do feel theoretically capable of having a healthy relationship now. I feel very much healed by having my own children. I don't know if I mean healed from that bad relationship, or healed from my unexceptional childhood, or just healed in a very broad sense of the various knocks and bruises of life.
I talk with my children a lot about how our family came to look as it does. Partly that's the current psychological fashion as I understand it (that kids can cope with pretty much anything provided they're given the recognition of their experience and the words to help them describe it), partly its a response to remembering my own inability to explain where the hell my dad was.
I do now feel slightly sad for my children that they weren't born into a big happy Waltons type family. I feel briefly envious when I see grandparents doting on their grandchildren, and I wish my DS in particular had other people to share his many and complex feelings with. But that's about more than just not having a dad, and perhaps fewer such families exist than I imagine, anyway.