Think a couple of siblings are hard to keep track of? Try to keep up when you may be one of 49.

It's a blustery October day in the town outside Indianapolis where Olivia Adams lives with her moms, Lori Adams and Patti Case, who are both ministers. The rust-red farmhouse-style home is surrounded by corn fields on one side, and a neat green lawn on the other.

Olivia is carving a pumpkin, as many do with their siblings around Halloween time. Next to her is her half-sister, Kinsey, who lives with her own birth parents.

It's like any other seasonal family gathering, except in this family Olivia and Kinsey have a lot more siblings, at least 47 other potential brothers and sisters that they’re aware of — but they can't really be sure.

Gathered in the kitchen are Adams and five of her half-siblings who traveled from as far as Chicago for what has become an annual tradition. This year, apart from Olivia and Kinsey, there’s Jack, Kel and two full siblings, Luke and Rachel Holsinger — all of whom share a single anonymous sperm donor.

"He was a farmer who spread his seed far and wide."

This is the third consecutive year that the Case-Adams family has hosted a "sperm donor sibling" reunion at their home to spend a day together carving pumpkins, sharing a meal, roasting marshmallows, playing baseball and charades.

And talking about what they tell people who ask about their dad.

"I just tell people he was a very busy man," said 14-year-old Kel Shamley, who attended with his mom and grandmother.

"He was a farmer who spread his seed far and wide," says 18-year-old Kinsey Presley-Hornung, who lives in Bloomington, Indiana, and has the light brown hair, green-brown eyes and nose shared among her siblings.

"Olivia has known from the time that she could even ask any questions that Lori was her birth mother, and that I'm her other mother and that through the modern miracle of medicine, she was conceived," says Case, her mom.

"I think it's just really helpful to have the support we get from other people whose families are kind of configured the way ours is," Case said.

But Adams didn't always know there were other families like hers. She saw a program on television about a Donor Sibling Registry that, for $75, helped her find several half-siblings in the area.

"I was like, 'Mom, you have to come watch this,'" Adams said. "What if I could find my siblings through this?"

In the United States, there is no government policy that limits sperm donation frequency or puts limitations on the potential number of offspring from the same donor, nor is there reliable data on the number of children born by sperm donation each year. According to the American Society for Reproductive Medicine, or ASRM, the number is likely higher than those conceived by in-vitro fertilization, approximately 60,000, according to the CDC.

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There is some concern among experts about accidental incest, the possibility that genetic disorders could be spread more widely, and other consequences of overusing one donor. The count of siblings Olivia and her moms use is based on 47 reported pregnancies from the donor, and includes two known sets of twins.

"How many potential people out there are half siblings that she could fall in love with?" said Lori Adams. "I wish that the regulation was stronger. I wish that information sharing was greater."

The only major database for sperm donors orsiblings born via sperm donation to find one another or share genetic or health information is the Donor Sibling Registry, a website founded in 2000 by Wendy Kramer, who had a son via sperm donation.

It can be harder than people think for a donor child to find his or her father after turning 18, Kramer said. Not every donor updates his records, which could have direct effects on the child’s health.

"If Olivia, for example, has some kind of health problem, is there a way for me to do research on some genetic background?"

To date, the DSR has connected more than 12,500 half-siblings and donors, but the massive demand hasn't been easy for Kramer to maintain on her own. In the United States, sperm clinics do not report to each other, and often donors do not keep their medical records or contact information updated. Kramer argues that this lack of oversight or regulation is a disservice to families that conceive via sperm donation.

"It's an active fight," said Kramer, referring to her efforts to push the reproductive industry for more regulation.

The lack of easy information can raise a lot of questions for donor children and their parents.

"If Olivia, for example, has some kind of health problem, is there a way for me to do research on some genetic background?" asks Patti Case.

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Right now, the answer is mostly no. While the FDA does screen sperm donors for infectious diseases and require a recent physical exam, the donor's identifying medical history is not provided to recipient families.

"You know how food companies have to put every ingredient on the back of a box, just so you know what you're getting yourself into?" said Presley-Hornung. "I mean it's essentially a product, this genetic coding is a product. And if you're giving it away, people should know that this might happen. This might come with it."

The American Society for Reproductive Medicine does release guidelines that put limitations on the number of offspring that can be conceived by sperm donation, according to ASRM spokesperson Sean Tipton. But they're guidelines, not law.

Judith Daar, the chair of ASRM's ethics committee and a professor of law at Whittier Law School, questions whether it would be appropriate to put limits on sperm donors.

"I don't miss having a father, because I never really needed one. He's kind of like a relative who died way before you were born."

"Could a similar regulation be enforced in a natural situation? Would we tell people who want very large families to restrict the number of offspring?" said Daar. "I think we would not favor the law limiting the individual’s ability to procreate naturally."

Others see potential advantages to providing donor children and their parents with more information on their genetic background, and some are in favor of limits on how sperm donations are used.

"I think that allowing donor-conceived offspring to be able to have information about their donors is critical, and I think we need to establish as a country a limit on the number of offspring that can be produced from one donor," said Professor Naomi Cahn, a family law specialist at George Washington University. Other countries, including the Netherlands, Australia and England have put limits on how many times sperm from a single donor can be used.

But the ASRM's Sean Tipton doesn’t foresee the federal government establishing a sperm donor registry.

"They don't want to spend the money, they don't want the hassle," says Tipton. "Before you are going to regulate people's reproductive choices, you have to have a really good reason. I don't think you want to jump in on a legal solution where it's not certain what the long-term consequences would be."

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Most of the donor siblings are curious about their genetic father, but don't yet feel an urgent need to meet him.

"I don't see this man as my family. But I do see him as part of my genetic identity. And therefore, I would like to see what he looks like, what he's like, just meet him, and let him know that we're out here," Olivia said.

"I feel like a really big misconception is that we kind of lack something," says Kinsey, who came with her moms. "I don't miss having a father, because I never really needed one. He's kind of like a relative who died way before you were born. You know you're related to them, but there's nothing to really miss."

"I think we are a traditional family ... Both in my immediate family and in this donor sibling family."

And in fact, many of the parents gained more family than they expected by conceiving with help from sperm donation. Danielle Hornung, Kinsey’s mom, says it never occurred to her when she started thinking about sperm donation that she would have a group like this.

"This I never dreamed of," says Hornung. "I knew she would have a family, a very good close family, but I never thought that it would include this."

And like a lot of siblings, what they really love is to tease each other, especially as they roast marshmallows around the Case-Adams family fireplace.

"It feels good to be around people that I can call my sisters and brothers," says Jack Wildman, who came with his moms, Jamie and Donna. "I feel a connection with them. The entire day. It's like dealing with other mes."

As evening falls and the light outside fades, the siblings light their Halloween pumpkins one by one. Olivia has even carved "a conception scene" complete with sperm and egg on her pumpkin, with "thanks" and the donor number in bold letters.

"I think we are a traditional family," Olivia says at the end of the day. "Both in my immediate family and in this donor sibling family, we have love and support and nurturing for one another. And that's all you need to make a family."