Sisters Find Out Their Baby Sibling’s Gender By Eating Cupcakes, But It’s the Littlest Girl’s Reaction That’s Making This Video Go Viral

Our first favorite sibling story of the year actually began took place last Christmas, though it only recently began touching hearts around the world. You'll love the emotional moment a foster child opened a present containing a stack of documents--and realized they were adoption papers stating that he, along with his little siblings, were officially joining their foster family forever.

The best moment of sisterly bonding this year? We say it was when the littlest of these three sisters woke up from her nap and joined her bigger siblings as they rocked out to the beat of a funky 1980s song. This family had obviously listened to this song before; it seems everyone knows just what to do when those familiar sounds start playing!

Who could ever forget this little girl's adorable visit to the hospital to meet her new brother? When you see the sweet tot's confusion turn to excitement upon seeing her newborn sibling, it's nearly impossible not to smile.

Not every amazing sibling story involved humans! Take a look at these delightful kitten sibs, two of whom are trying their best to get the other fuzzball to play. So sweet!

Not to be outdone by cute kittens, this pile of pitbulls is also showing us an endearing display of brotherly love. The grumpy big dog is clearly taking his time warming up to his role as big brother to his many, MANY new younger sibs.

It was a year for cute pregnancy announcements, but this one makes our siblings list because of the clever way the New Jersey family included big bro and sis in on all the gender-guessing fun.

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The most aww-worthy display of sisterly love came from curly-haired Jessica, who was tickled pink to take on the role of big sister. Check out the way she expertly soothed the cries of her new baby sister, Vanessa. Sisterly bonding at its best!

One of the year's BEST big brother moments came from this 5-year-old British boy, who had the happiest reaction ever to learning that his only-child status was about to change. Couple his enthusiasm with his charming accent, and you've got a heartwarming video that gets cuter as it plays.

Our win for dramatic sister story of 2015? The tale of Holly Hoyle O'Brien and Meagan Hughes, both of whom were born in South Korea and later adopted by American families. After 40 years apart and a 7,000-mile relocation, these two orphan sisters finally found each other in one of the most bizarre, cases of coincidence we've ever heard about.

But the winner for all of 2015 may have to be the reunion of seven long-lost adult siblings--brother Jacob and sisters Mary Anna, Becca, Lisa, Rebekah, Meghan and Lesly--who gathered in Los Angeles this summer and celebrated their first time all being together in the same room by posing for some clever, child-like photos.