Where were you when you realized Elizabeth Olsen was the younger sister of Mary-Kate and Ashley Olsen?

As noted OTCU (Olsen Twins Cinematic Universe) historians, we've known that fact for quite some time. But for some WandaVision fans, discovering that connection between the trio was mindblowing. And they are far from the first familial reveal to make people say, "Wait, whaaaaaa?" So in honor of National Siblings Day (April 10), we're looking back at all of the celebrities you may have forgotten have shared 23andMe data

Did you know Kate Middleton is actually part of the same family tree as two of Hollywood's most famous sister duos? Or that an iconic sitcom star is Jason Sudeikis' uncle? And how about that Lenny Kravitz gets a mini-family reunion every time he stops by Today?

Of course, we included some surprising sibling pairings too, which include Jonah Hill and a Game of Thrones star.

Let's revisit some celebrity fam connections, shall we? 

The rapper and Fast & Furious franchise star is cousins with the R&B singer thanks to her stepfather, Reverend Edward Best, who happens to be Luda's uncle.

The late-night host and the Rescue Me creator are third cousins.

The onetime Grey's Anatomy doc has called the legendary director stepdad ever since he married her mom Kate Capshaw in 1991.

The "Ex's & Oh's" singer is the SNL vet's daughter, born from his relationship with former model London King.

The Grown-ish star calls the rapper her second cousin. She was even the flower girl in his 2005 wedding with now ex-wife Kelis!

The star of The Politician is also the daughter of the Back to the Future icon.

Not only did the Veep vet make a name for herself playing a famous daughter on the HBO comedy, but she's also a famous daughter in real life. The erstwhile Jack Bauer star is her father.

Some Emily in Paris viewers were très shocked to discover Lily is the daughter of the English Grammy winner. 

The comedian and the New York Senator are actually related, as he's the first cousin of her father.

According to a 2014 People interview, a family historian from Ancestry.com claimed that the Fannings and the Duchess of Cambridge are all descendants of King Edward III, who ruled England from 1327 to 1377, making them very distant relatives—21st cousins, to be exact.

The actors are actually brother and sister!

The SNL alum calls the Cheers icon Uncle George whenever he seems him. At least, we assume he does.

Yep, Game of Thrones' Stannis Baratheon is the real-life dad of Fear the Walking Dead's Nick Clark.

The brunette beauty and the soulful "Stay With Me" crooner are third cousins. During a radio interview, Smith admitted that the pair have never met because their family is "huge."

The Salt actor and the memorable Law & Order: SVU guest star are half-brothers.

You may not have guessed but the Bridesmaids comedian and The View co-host are cousins.

The gorgeous British model is the eldest child of the Bush lead singer. The father and daugher first met when Lowe was 14 after she requested a paternity test. 

The We're the Millers actress has the perfect mentor in the Pretty Woman star, who happens to be her auntie.

Who knew the stunning Dancing With the Stars pro is second cousins with the Friends star?

The sexy True Blood vampire caught the acting bug from his dear old dad who stars in both The Avengers and Thor franchises.

The Ghost Rider actor comes from an extremely talented family. One of his cousins directed The Bling Ring, the other starred in Saving Mr. Banks and his uncle directed The Godfather.

The outspoken British singer is the older sister of the Game of Thrones star. She even wrote a song about him titled "Alfie." 

The Damages star and the Lipstick Jungle actress are second cousins.

The Secret Life of Walter Mitty actress originally inspired her baby brother to get into show business.

The gorgeous Parks and Recreation actress is the daughter of the legendary music producer.

The Lost actor has a very famous cousin in the Mission: Impossible action star.

The "Drop It Like It's Hot" rapper is first cousins with The Game actress and her brother, Ray J.

The Anger Management star is the youngest brother of The Breakfast Club actor.

The Twilight actress probably gets great career advice from her pop, who directed Rush and A Beautiful Mind. 

The Today show host and the "American Woman" rocker are distant cousins.