I tend to agree with late 19th century fictional American philosopher William Munny, who said "Deserve's got nothing to do with it."
Seems to me nothing we are and nothing we can do makes us deserve another human being - whether we're talking offspring, or soulmate. The best we can hope for is a chance to luck into; the best we can do is justice to the chance that comes.
Every person and every relationship in my life, bonded to me by blood or by love - honestly, I lucked the fuck out as far as I'm concerned. I hope I have the gratitude and humility necessary to make good on the chances I've been given, which I do not and could never have deserved.
Of course, I can see why we might want to criticize parents (or lovers, or spouses) who have done a terrible, grossly negligent job. Who shat on the chance they lucked into - the chance to be possibly, the most important person in another human being's life.
But that's not saying the rest of us, or any of us, deserve such a chance. It can't help us to treat such chances as if they were based on merit, or entitlement. Anyone who gets a chance like that is damn lucky. Anyone who gets that chance should be grateful for the opportunity to prove they can do right by the person who now depends on them. Ultimately, to have a child, or to have a love, is to hold a sacred trust. Such a trust as that can never be deserved. It can only be earned.
Just being here on Earth is a chance we cannot claim we deserved. None of us (as individuals, at least) deserved at all to be born. Our unique DNA was the result of some one damn sperm out of thousands, beating his ballmates to the finish line in a mad scramble. Any of us could have easily been edged out, by some other individual - a completely separate, distinct individual. Someone to whom the individual we actually are would stand in a relation far more like sibling than self. Which is only one of the billions of accidents that led to any of us being here!
No person can claim they deserved to be here. Those of us who happen to show up, best we can do is try to use the life we have to earn our hold on the place we carved out for our life, and on the trusts which we have been lucky enough to be given. Best we can do is justice to the chances we undeservedly got. As noted Kiwi rabble-rouser Dave Dobbyn put it, "You pay for your life with your life."