People always think that people who are only children are a tad 'weird' which struck me as bizarre - why would not having no brothers or sisters make you this way?

Ok I can recognise 'only child syndrome' i.e an unwillingness to share, in people who have siblings as much as only children, but is that enough in itself to make them weird? I have three close friends who are only children and I don't find any of them to be in the slightest way odd, in fact I've found them really faithful friends, so is it perhaps not exactly true to say that people with no siblings are 'nutters'?

Surely its just some sociological study waiting to happen?