Saw a curious thing while looking at Saint Tetrimon's
article on the evelopedia.
"Inire Ardishapur was born to the Ardishapur Family in 21346 AD"
"In 21403 AD, Inire's mother passed away from complications with another childbirth"
That's 57 years later. And Inire's mother had several miscarriages before Inire. So... maybe 60+ years, at a minimum, of reproductive opportunity, compared to ~25 for modern day women.
And consider too, that this was the Ardishapur family, the most religiously conservative, and thus, the least likely to be using weird wibbly reproductive medical technologies.
So, True Amarr women, unlike many others in New Eden, have many decades in which to have children.
And so, someone being the 15th, or even 30th son of someone, may not be too far fetched.