Ken Allen, 59, from Adelaide, SA, shares his real life story:
Walking through the hospital corridor, I heard the sound of countless newborn babies crying.
The noise might have been shrill and deafening to some, but as a teacher of midwifes and father of two, I knew how much joy babies brought to their parents.
I was also well aware that there were countless couples who, try as they might, just couldn't conceive.
This knowledge played on my mind often until one night, I sat down to talk with my wife, Sue.
"My heart bleeds for these families unable to have kids," I told her. "We're so lucky to have Leah and Marcus. I want to help."
Sue, a midwife herself, nodded with understanding.
"If there's a way we can, we should do it," she said.
After some research I decided to donate my sperm.
I was 30, in good health and passed the preliminary medical and counselling checks with flying colours.
At the time, the law prohibited sperm donors from having any contact with their donor children, but I knew this could change over time.
So when I filled out the forms, I included an inspirational quote that I'd always referred to throughout my life:
Man cannot discover oceans unless he has the courage to lose sight of the shore.
I figured that if any of my donor children wanted to find me one day, that might be a clue that I would welcome them.
In just over two months, I made 20 donations.
I didn't think much about it until two years later, when our family was moving interstate.
I called the clinic to update my contact details.
"There haven't been any successful pregnancies from your donations," the office told me.
I felt like I'd been punched in the guts.
"It was all for nothing," I told Sue afterwards. "You never know what might happen down the track."
"Don't say that," she reassured me.
We went on to have two more children and watching our kids grow into adults filled me with pride.
But sometimes when I was out and walked past teenagers with my hair or eye colour, I'd wonder if they might be from me?
It was possible that the hospital had made a mistake, or that one of the couples had finally fallen pregnant.
Yet years passed and I heard nothing.
Then, at 54, I started to experience muscle aches like my whole body was stiffening.
My left hand was barely moving at all.
"You have Parkinson's disease," he said.The words sent an arrow through me.
I'd worked in hospitals long enough to know that Parkinson's was a neurological condition that robbed people of their speech and movement.Worse still, it was hereditary, which meant my children were at risk, too.
I was told I might have another 10 years of reasonable health before I went downhill completely.
Later, I found out I also had heart and cardiovascular issues.
"You're strong," Sue said. "We won't let this beat us."
I tried to get on with life as best I could.
Until, four months later, I received a letter from the sperm donor clinic, asking me to call them.
So I did during my lunch break at work.
"Are you sitting down?" a woman asked.
What was all this about?
My whole world spun as she revealed I had been the donor of 11 children: two girls and nine boys.
"But …" I stammered. "I was told I wasn't successful."
"I don't know who told you that," she checkled. "You've been quite successful!"
It turned out some of the children, who were now in their twenties, wanted to contact me.
As legislation had changed, they were allowed to know who I was, provided I agreed.
For seconds, I was too speechless to reply.
All those years I thought my efforts as a sperm donor had gone to waste, when really I'd given 11 different couples the children they yearned for!
Now I just had to break the news to my family.
I knew Sue would be supportive, but the kids didn't know what I'd done over two decades ago.
I worried they'd be embarrassed.
"I've got something to tell you," I began as we sat round the table that night.
Thankfully they were all stoked when they learned about my secret.
"We've got more family!" they cried.
I wrote an email to my donor child, Chloe, 25, who'd been searching for me for years.
I'm very happy to have contact with you, I wrote.
I'd love to have an ongoing relationship.
The clinic forwarded my email to her.
She replied almost immediately and we started talking more and more.
I knew I had to tell her about my Parkinson's, but that didn't deter her from wanting to meet me and my family.
Weeks later, when she flew from Melbourne and Adelaide, we were all waiting at the airport.
At first all we could do was hug.
It was the strangest feeling to meet a child you never knew you had!
But Chloe hit it off with the whole family and we stayed in contact.
She put us in contact with 26-year-old Melissa, my other donor child who she'd managed to track down.
Mel's dad had passed away and she was finding it hard to process the fact that I was her biological father.
I felt incredibly sorry for her.
"Your dad loved you very much," I consoled her. "Whether you decided to meet me or not, he'll be proud of you."
I was glad to gradually develop good relationship with her, too.
Since then, two boys, Robert and Nathan, both 25, have also come forward.
Meeting Robert was one of the most surreal experiences of all: he was the spitting image of me!
Just a few months ago, the four of them joined us for one big, extended family get-together.
It was an amazing feeling.
In the meantime, I'm continuing my search and hope to someday meet my other seven girls before it's too late.
Chloe's even making a film about my life, in case I don't get the chance to find them.
I want them to know that I love them and that they're part of my family too.