One problem only children can face is smothering parents. I often longed for a sibling so I wouldn’t be blamed for everything that went wrong. I could only point to the dog, which wasn’t convincing.
While I never really wanted a sibling, but I did suffer from too much attention, mostly negative. Since it would seem natural for parents of only children to invest heavily in the child, I would just encourage parents to give only children some space to breathe.
Can’t beat the Schwaben. The best people on earth. Also spätzle.