First-time breeders who are overly proud of their success.
There are some feats so amazing they seem at first to be impossible. There are some achievements that seem ordinary only because they happened long ago. There are some things that require a lot of skill even if they're not mind-bendingly difficult.
Reproducing, however, is something so basic and so unskilled that being able to do it is inherent to all life by definition. Yet many humans who successfully reproduce act as though this were some amazing achievement that no one in the history of the planet has ever even dreamed of, as opposed to something slime moulds can do.
I'm not saying you can't love your offspring or even that you shouldn't have any; just don't act like producing them was some mystical magical thing that defies our very notion of what's possible. And definitely don't try to claim you're somehow better than me for having done it.
If you tell me that I'm incomplete for not breeding or that I'm missing out on something sooo wonderful or amazing, then I am going to invite you out to your favourite restaurant on a day I know you can't get a babysitter.