Taylor Swift is now officially part of the wolf pack -- the Haim wolf pack, that is.

The pop star posted an oh-so-adorable video of the four singing along to Faith Hill's "This Kiss," along with a caption thanking sisters Este, Danielle and Alana for adopting her into their family. Of course, Taylor has several besties, but this sister trio has made their way into Taylor's inner circle pretty quickly. And why not? They're funny, stylish, their music is awesome and they promote serious girl power.

In honor of Taylor's induction into the wolf pack, we're decided to take a long look back at how these California girls went from Swift's fellow pop stars to long lost sisters. Oh, and not to brag, but I think MTV kind of had something to do with it.

Haim Predict Their Friendship: March 16, 2013

We ask everyone at the 2013 mtvU Woodie Awards who Taylor Swift should date next. Instead of rattling off a list of men, Alana says this: "TT Swift, don't date someone else. Come out with us and we will party and we will be together as girls, be merry and we don't need guys. Girl power."

A Twitter Friendship Begins: October 29, 2014

Haim tweet their love of a T. Swift song, which causes a celebratory dance and the beginning of an online friendship.

First Photo Of The Foursome Surfaces: December 5, 2014

Taylor gives us photo evidence of the budding friendship, while giving Haim a shout-out for their Grammy noms.

A Part Of The In Crowd: December 13, 2014

You know that you're part of Taylor's circle, when you're not only invited to one of the most A-list parties of the year, but you're standing right next to her as she blows out her birthday candles.

Bringing Sexy Back Is A Group Effort: Dec 15, 2014

Taylor brought her girls with her as they danced the night away, alongside Beyonce, at Justin Timberlake's concert.

Dad-Approved: January 9, 2015

You know it's a forever friendship when Scott Swift approves.

Golden At The Globes: January 11, 2015

It was a girls' night out as Taylor, Haim and Jamie King, hit the red carpet to show Lorde some love as she was nominated for a Golden Globe.

Let's Get Leid: January 23, 2015

The fab four took off to Hawaii for a girls-only vacation. They went whale-watching, wore Bill Murray sweatshirts and were there when Taylor showed the world her belly button.

Road Trip: Feb 1, 2015

Haim were announced as a special guest on select dates of Taylor's upcoming 1989 Tour, and they're bringing the fire.

Taylor Brings The Laughs: February 8, 2015

Not only is Taylor the perfect BFF, she's also "hysterical." Seriously, is there anything this girl can't do?

Who Run The World? March 8, 2015

Haim hung out with Taylor, Selena Gomez and Ellie Goulding on International Women's Day and had a tea party. Guess my invite got lost.

Welcome To The Wolf Pack: March 14, 2015

Taylor showed Este some b-day love with this video, and a heartfelt message about how her "life has never been the same" since the girls adopted her into their "wolf pack."