Selfish just having one?! What a load of bollocks. It's far more selfish for parents to keep having kids just because they want to have lots of kids, without considering the impact on the existing child or children. Even having no. 2 can be selfish when Dc no. 1 is taken into consideration. And the world is already overpopulated, so even having one child is technically selfish in terms of the world's resources, etc.
Am not saying that people shouldn't have however many kids, or none, just putting another side of the argument over.
My son will be an only child. It disgusts me that there are people so inane and immature that they would pronounce me a worthy mother of an only, or a selfish one, based purely on the reasons why he is an only.
As for me, I loved being an only child. Then my parents had another child, a sibling with massive behavioural difficulties which dominated family life and all their attention. I've had to have therapy for how shit my life became after he came along. Do I love him? Yes. Would my life have been better if I'd stayed an only child? Also yes. I realise that this is not going to be everyone's experience of such a sibling, but it's not unique to my family either.
There is no one size fits all. All I ask, like most parents of only children, I'm sure, is that people stop making/asking tactless fucking comments and questions about only children. People just love to go on about how an only 'must' have a sibling, etc., etc., to someone who might be severely depressed because they can't have another child. Or just to someone whose choice to have one child is as valid as any other family-size choice.