The thing about soulmates is that they don't have to be romantic. Google literally defines "soulmate" as: "a person ideally suited to another as a close friend or romantic partner". For the purposes of this article, we'll be focusing on the "close friend" portion of the definition, because when your best friend is also your soulmate - it just so happens to be the best thing on this Earth.
Best friends are there for you, know how to make you laugh, make time for you, and most importantly - feel comfortable just being themselves around you. Soulmates, however, complement each other. You don't find them often, but they are somehow completely different and the exact same as you. They're up when you're up, and down when you're down. This type of friendship cannot be taken for granted; you're lucky if your blessed with one in a lifetime, let alone two or three.
Maybe it's a personal thing - but I've always thought that loving someone, and being in-love with someone were completely different. To be in-love with someone meant that you wanted to spend your life with them in the romantic sense - marriage, babies, bla bla bla. But to love someone just meant that you cared for their well being over your own; it didn't have to be romantic. Best-soulmates love each other, they FaceTime with you just to talk and do homework, drag you out in the dark of night to get nachos at some restaurant neither of you had been to before, maybe even say "I love you" before hanging up the phone. These are the friends you don't let go.
TV shows like Grey's Anatomy and Friends have described it best. The relationship between Mer and Cristina was epic in the sense that while it was platonic, they were somehow made for each other. Meredith was in-love with Derek, but she loved Cristina. The same was for Monica, Rachel, and Phoebe. The three of them had this connection even though they were all so different. They were all in-love with their boyfriends (and eventual husbands) but the three of them loved each other more than anything.
If you're lucky enough to have a best-soulmate, you can understand what I'm talking about. You can have full conversations just by looking at each other, you know what the other is thinking about because you've shared every thought you've ever had with each other, saying that you can read each other's minds' is a pretty bold claim, but I bet you every cent in my wallet that you've thought it at least once. I know for sure I have.
Best-Soulmates are incredible, you can trust them with anything. They're the people you call to hide a body, plan revenge against an evil ex, or spend all day lounging around because you'd rather be with them than alone. They're the one you call when you land a job, when you failed a test and you need someone to prevent the on-coming breakdown, who you tag in all the "relatable" Facebook posts. They're the ones you'd do anything for, the ones you love like family, and the ones you'd be lost without. They're the yin to your yang, the Cristina to your Meredith, your soulmate.