Growing up as an only child in the 1950's and 60's, Susan Simon never questioned that her loving dad, was anything but her biological father.
"I asked my dad, 'Why didn't you have more kids?' He said they had trouble conceiving," she said.
But that wasn't the whole story, a story that didn't reveal itself until last year, more than 60 years after Simon was born.
That's when Simon, who lives in Oakland, decided just for the fun of it, to send a DNA sample to an ancestry website.
"There was a fathers day sale on 23andMe, so I thought now is as good a time as any. So i did the test," Simon said. "Six weeks later I got the results."
And when those results came back?
"At first it was a shock. And a little numb. Then a lot of gratitude," she said.
What Simon learned from those results was that she was definitely not an only child, but had 14 half- brothers and sisters. That number that has since swelled to 35 siblings and counting as more matches keep coming.
It turns out her biological father was a serial sperm donor with a career that spanned more than 25 years.
"I know he was a doctor and lived to the age of 90. He wasn't a med student when he was doing this," she said.
She doesn't know why her biological father did what he did, and why he donated sperm so many times. "I was numb for about 10 days, trying to sort through my feelings. I kept trying to see if i was angry," she said.
But she wasn't angry. Quite the opposite.
"I got excited. What a gift at this stage in life to suddenly find a new family," she said.
Some of those new family members held a reunion last year.
"How cool is it to meet these people you all these things in common with. It was great," she said.
But she says some siblings have shown no interest in keeping in touch. One half brother told her he found what their biological did was wrong. "I think he feels to donate so many times is immoral," she said.
Simon's mother died when she was a teenager and never spoke to her about it.
Her father, the man who raised her, died in 1997, never saying a word about it either. For Simon that's OK.
"For me at that time ignorance was bliss," Simon said. "And then finding out now is just so much fun."