They were, after all, a family. None looked like their redheaded mother, Goldie, yet the pups were so similar I could only tell the brown fur-balls apart by their numbered collars.
Besides, they had so much fun together. A couple would start to wrestle and the others would come running, to watch or join in. The largest and the smallest were inseparable, curling up together when they slept. They all spent countless hours playing their own versions of hide and seek and king of the castle.
When it came time to send them to their forever homes, we tried to lessen our loneliness by adopting one. We named him Simcha, the Hebrew word for joy.
Still, three months later, I was thrilled when an email arrived inviting us to a puppy reunion.
"I was curious to see how they would do with each other," said Elise Branson, who arranged the gathering that drew Goldie and five of her then-5-month-old pups. They ran and played like old times.
"They definitely got along," Branson recalled. "I don't know that they would have done that in such a large group if they weren't that well-bonded."
Once they leave the litter, however, reunions like this might be more for the owners than for the pups.
A study into kin recognition in dogs, conducted by Peter Hepper, a psychologist at Queen's University of Belfast in Ireland, found that puppies could recognize their siblings' smell for the first month or so, but by two years, if they were living apart, that was no longer true. (They could, however, still recognize their mother's scent and vice versa.) He didn't test for recognition in the interim, so it's unclear when the memory of their littermates starts to fade.
I had so much fun seeing the pups romp together at the reunion that I started a Facebook page for the owners. Every few months, someone posts a photo or an update. I know, for instance, that the puppies now range in weight from 70 pounds to more than 100 pounds. One owner shared her pup's genetic testing, which determined that Goldie is part American Staffordshire terrier and part Cardigan Welsh corgi, while the pups' dad was a German shepherd.
Other dog owners have similar pages, especially those who have adopted retired racing greyhounds, since their lineage is more easily traceable. The site www.facebook.com/Greyhound.Littermates.List claims it has helped reconnect 1,500 siblings in the past 16 years.
Of course, there is a difference between reading about your pet's siblings and watching them hang out together. So it's especially exciting for me when we run into Simcha's sisters, two of whom frequent the same dog park.
Their owners met when they happened to adopt their puppies from Animal House Rescue in Fort Collins at the same time just before Christmas 2013. Unbeknownst to each other, they named the puppies June and Juna. Since then, they've arranged get-togethers, often a few times a week.
"They truly, truly love each other," said June's owner, Bonnie O'Brien, 32, a small-business owner.
The dogs have a ritual greeting when they meet: They run a few laps and then settle down to play, never leaving the other's side.
"They play in a unique way too," she said. "It's strange to watch them. It's more like they're having a conversation. They will lie down and just pat each other. It's really gentle when it's the two of them. When she's playing with other dogs, it more roughhouse. This is definitely different."
The research suggests that dogs who live with a sibling into adulthood seem to recognize their brother or sister's scent, Hepper said. Because June and Juna have stayed in touch regularly since they moved to different homes at 8 weeks old, they might indeed know each other as siblings.
Like humans, however, not every family relationship is a smooth one.
"I've known dogs who were siblings and they wanted to kill one another," said Dr. Nicholas Dodman, founder of the animal behaviour clinic at Tufts University School of Veterinary Medicine, in Boston.
Fortunately, that doesn't seem to be the case for Goldie's brood of 13 (nine fewer than the Guinness record.)
So I don't know about Simcha, but I can't wait for the next reunion.
For photos of Goldie and her puppies, go to www.facebook.com/JPuppies
Greyhound littermates: http://www.littermateslist.com