Influence of opposite-sex siblings on social behavior...?

My mother once told me that part of the reason why some people tend to be shy around the opposite sex -- especially peers, even platonically -- might be linked to the person's upbringing when it came/comes to family. She spent much of her childhood with her older brother, so the male-female bonding was not in some way a disconnect for her. On the other hand, there are many people -- myself included, who haven't had those experiences because of being the only child/son/daughter in the family.

This is not to say that because one is the only child, shyness is an inevidably and inherited trait, but as a male in society who was brought up as the only child, I cannot help but feel that the lack of "practice" has had an influence on the way I interact with someone of the opposite sex.

Social experiences will shape one's personality, I suppose this is no different. Of course, genetics account for about 50% of one's personality, so it's a mixed bag.

Having sisters to interact with, may help some out with being less shy with girls. But I don't know if it's everything either.

Just as a side note: I am an only child and both of my parents are extremely shy introverts. That puts me in a very unfavourable light, either way. But yet, I'm far less shy and introverted than either of them... except when it comes to beautiful girls. But I'm working on it.

I only have a sister, and I don't feel like my ability to interact with men is any lower than my ability to interact with women. I am shy in general, but I think that is more due to my having a VERY introverted father.

Hmm, I just remembered something. Before my parents divorced, they had taken in a niece who was from a really bad background. She lived with us for the first 6 or 7 years of my life, and I actually thought of her as my sister, in many respects. She was about 10 years older than me, so we were apart age-wise, but it wasn't that different from having a real sister, IMO. So I'm not sure what to think now...