I have thought about how to answer this odd question for some time now. Yes is the short answer. I am the oldest child in my family. My father, uncles on both sides (genetically it is from both sides in my branch of the family) and my grandfathers were all extremely endowed.
It became a problem when I was growing up and hit puberty. My flaccid size which was always big when I was younger became "worse" and was "distracting" and involuntary erections were extremely embarrassing and caused issues at school, so my parents, with the consent (and apparent relief) of the school took me out to teach me at home with the school systems help. You have to remember this was long before there was such a term as "home schooled". I actually studied the same lessons and homework with the same books as others my age in school, but did it at home. Teachers provided lessons and assignments to my parents. Sometimes I would meet a teacher at our house, her house, or school or the library (it varied over the years with teachers) to take a test or later an exam that they wished to give me and not have my parents proctor. I turned in homework to my parents and usually they just turned it in to the teacher(s) and I got the results back later and the same with tests. They gave a test to my parents, I took it, and they gave it back to a teacher(s) to be graded. This went on until I "graduated" even though by the time I was a "junior" or "senior" I could reasonably control my erections though my flaccid size was still a problem. Anyway, so my parents were very aware of my endowement while I was growing up.
Like a few of the other posters above, it also happened that I got "lucky" during those years often with women who if not "friends" with my mother, they probably at least knew her and she them. Some I think did not know her and she them. Then again some of those women I had some experience with while growing up had also been with at some point prior to meeting me some older relatives of mine (uncles, one grandfather in particular, and sadly, my father). During these teenage years I had sex of one form or another with quite a few women who were very aware that I was uniquely endowed long before they got my pants off.
Was my mother aware of some of this. Yes, but mostly generally speaking she knew I was having sex but not with whom. She did suspect, I think, some women, but she also suspected (in retrospect) or knew outright, that my father had also been with some of these women. Of the couple of women that she absolutely knew about, she, and my father, were concerned that I would get someone pregnant and very concerned that I would have some bodys husband catch me and they would be going to my funeral. One woman in particular I remember she was upset about because of this and her husbands prior experience with my father and his wife (apparently I much later learned she and her husband had had a 3sum with my father and this man was upset that while he was very endowed, apparently he did not like seeing that my father was bigger and what started out as fun "bet" did not end well). Anyway, I suppose that answers the original question and the followup comment/question that was posed? | 
Nice Thread
