I Am Fascinated By Human Behavior

Is anyone on here an only child? If so what has your experience been, especially as an adult? Do you struggle with waiting your turn because you always want to be first, the give and take in relationships because you can only see things your way, considering another's point of view, or losing in a competition. I ask this because I've always heard these things are particularly hard for an only child. It might be true because a cousin of mine who's an only child has had two failed marriages because she just can't understand why people don't put her on a pedestal like her parents always did.