I guess my family opted for the skip-a-generation approach
My grandfather, by all accounts, was considered well-hung, and was very open in showing his body.
My father, on the other hand, is below average length, and has spent a lifetime of hiding his body away and in many ways, sadly, repressing all thoughts about sex and sexuality.
Since I'm an only child born to parents who are both only children, there isn't exactly a huge number of family members to compare against, to say the least.