Ken Allen knew he was a very lucky man.

He had a loving wife, three beautiful children and an adopted daughter from Taiwan.

But it broke his heart knowing other people aren't so lucky, so asked his wife Sue if he should become a sperm donor.

Sue agreed, and in the next few months Ken, who lives in Melbourne, Australia, visited a clinic and donated, with the hope he might be able to help other couples desperately trying for a family.

He knew he wouldn't be able to contact any possible children, but decided to leave them a secret message on his two-page donation form in case they ever wanted to find him.

In an interview for a new documentary with Australian TV show Sunday Night , Ken said: "I knew that there was a possibility that one day an offspring may in future get a hold of this, and I really wanted to encourage them to pursue their dreams and also to perhaps pursue me."

On the form, he wrote: "Man cannot discover oceans unless he has the courage to lose sight of the shore.

“If you can, come find me.”

He carried on with his life, watching his own children grow into young adults, until one day in 2014 when he was on his lunch break at work he received a phone call.

It was the IVF clinic he had donated at several years ago, and the woman on the phone told him he had 11 children living across Australia.

He replied: "Well, I'm not a drinking man but I could do with something right now.

"Eleven, eleven, eleven, you've got to be kidding me."

He's now met four of his new children, including 25-year-old Chloe Allworthy, who had been searching for him for years.