After a vaery hard 18 months with DS1 who was high needs ( cried about 4 hours a day) with reflux, and refusing to be held, refusing to take bottle, and me ending up with PND....
I still wanted another baby. Somehow, deep inside me, I wanted another baby.
As despite all the hard stuff, it was also the most amazing thing. and despite him being "difficult" I loved him so much it was overwhelming.
Had baby 2, who happened to be easygoing and rarely cried.
I get so much pleasure out of their bond, seeing them as brothers, seeing DS1 being so kind to his baby brother. The whole sibling dynamic.
If anything, I wish we had had more babies! I am 40 now, so feel too old and decripit ( seriously bad back mainly) to start again. But I sometimes wish I had had 3 or 4!
Then again, I would never say anyone else should go for more than 1. Do what suits you, an only child fits in wonderfully into the parents lifes.I think a lot of " onlies" like being an only child.
Usually a second child is much easier than the first one though, as the parents now have the benfit of experience. So it will never be as hard as it was that first time!