A best friend should always have your best interests at heart, be a sympathetic listener and share their hard-won life lessons with you.
So, who better for a BFF than your 93-year-old granny?
That was the thinking of one particular grandson, 27-year-old social media giant Ross Smith.
Seven years ago, Ross - who shares content with his 2.7M followers under the handle @smoothsmith8 - filmed a clip of his fun-loving grandma blocking his shot during a basketball match.
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She's a demon on the court, that Granny Smith.
The moment propelled Ross and Grandma Smith into the spotlight, and they've been shooting and filming together ever since.
Today the adorable pair have a whopping 892,000 YouTube subscribers along with millions of followers across Instagram and Facebook.
The duo love a whacky themed costume and have dressed up for all the major holidays, from Christmas to Thanksgiving. Think turkeys outfits, pilgrim hats, Santa beards and Rudolph noses.
Elsewhere, Ross and his good-humoured gran have transformed themselves into a gangster duo, with diamond dollar sign chains and supersize boxy sweaters.
The pair love a movie tribute, and have remodelled themselves as Toy Story's Woody and Buzz Lightyear, with Granny.S rocking a Stetson and cowboy boots.
Then there was the time when the twosome paid tribute to Captain America and Avengers: Endgame - FYI, Grandma Smith isn't afraid of head-to-toe blue lycra.
But our personal favourite has to be duo's take on Pixar's tear-jerker flick Up, complete with a balloon-topped house, doting dog and Ross' super-gran dressed as adorable widower Carl.
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At the time of writing, the snap has an incredible 267K likes.
In an interview with Metro, Ross said of his granny: "We are best friends, we hang out almost everyday and travel the whole world together! We have been there for each other through all the good times and hard times."
This comedy duo are all the goals. We want a behind-the-scenes documentary, please.