A Florida woman born with the help of a sperm donor has discovered she has 40 half-siblings.

Kianni Arroyo, 21, first began tracking down her brothers and sisters when she was a high school sophomore in Orlando.

The oldest out of the enormous brood, Arroyo has discovered her siblings include four sets of twins, some living as far away as Australia, New Zealand and Canada.

"I was raised just by my mom, and she's always been honest with me about the fact that I was born to a sperm donor," Arroyo told Metro US.

"I always wanted to find out more about who I was, and whether I had any siblings, so as soon as I was old enough to access the records I did just that," she added.

She first became acquainted with her 20-year-old half-sister, Joanna, who lives close by in Tampa Bay. The women are close, and make arrangements to see each other every other month.

"When we meet, we hit it off really quickly and get on really well," Arroyo said. "Even though we've never met before, having a father in common gives us a really special link, and means we feel comfortable with one another."

Along with meeting most of her half-siblings, Kianni has also been introduced to her biological father.

Describing him as a "really cool guy," Kianni's father, who prefers to remain anonymous, has met with her three times, with the first encounter taking place at Universal Studios three years ago.

While most sperm donors are usually only permitted to donate between 15 to 20 samples, the company Kianni's father worked for was taken over, and the records were erased. Subsequently, he was allowed to repeat the same number of donations over again.

Arroyo plans on wedding her fiance later this year, and hopes she and her partner will be able to meet as many half-siblings as possible before they tie the knot.

She said meeting her half-siblings has been a fulfilling experience that has changed her life.

"I'm an only child, so I get the best of both worlds," Arroyo said. "I have my mom to myself and all the advantages that comes with that."

"But whenever I feel like some company, or spending time with family members my own age, having so many half-brothers and sisters gives you more options than most people," she concluded.

What would your reaction be if you discovered you had 40 siblings?