Happy Birthday, Ivy Seewald! Those well wishes may be a little belated, but Jessa Duggar‘s new daughter officially celebrated her ~birth~ day over Memorial Day weekend. The Duggars welcomed their newest addition — baby No. 3 for Jessa and husband Ben Seewald — on Sunday, May 26. But that date isn’t just notable because of the birth of the 13th grandkid on the Duggar family tree. It turns out that little Ivy actually shares her big day with someone very special: her great-grandma, Mary Duggar.

The family inadvertently shared the news over the weekend. Though the mom-of-three didn’t share her baby news until Tuesday, May 28, the Duggars’ official Facebook page hinted that something special went down. “May 26th is one of our very favorite days!” they wrote on Sunday in addition to sharing a birthday post for Jim Bob Duggar‘s mom. “Not only is it Grandma Mary’s birthday, but it is also Joy and Austin’s anniversary! Happy Anniversary, Joy and Austin! We can’t wait to see what all the Lord does in your family this next year! 😄” 

Though they didn’t mention Ivy, the new granddaughter had actually been born a few hours earlier. On the family’s blog, the parents mentioned that she’d been born at 5:57 p.m. CT, and the Facebook post went up around 8:40 p.m. CT. Grandparents Jim Bob and Michelle Duggar may not have wanted to spill the beans, but they clearly wanted to celebrate. We’re sure great-grandma Mary is celebrating, too!

Surprisingly, this is actually the first time anyone in the family has had to share a birthday — well, that is, other than the two sets of twins. Though plenty of them have come close, and there are lots of back-to-back birthdays, especially in May, everyone’s pretty much had their own day until now. That may not actually seem all that surprising, considering there are 365 days in a year and not quite that many Duggars (yet), but according to the birthday paradox, once you’ve got at least 23 people together in a room, there’s a 50-percent shot that two of them share a birthday.

When you add up Jim Bob and Michelle with their kids, sons- and daughters-in-law and grandkids, you’ve already got 44 people. According to the odds, it’s more likely than not that we should’ve already had some overlap on the calendar. As the family keeps popping out grandkids, there are bound to be even more shared birthdays over the years. For now, though, we’re willing to bet that Grandma Mary and Ivy don’t mind celebrating together. In fact, it’s probably pretty special for the great-grandma. Now, we’re just wondering if they’ll also share a party next year.

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