You know their wardrobe inside-out.
Despite being intelligent as individuals, you’re truly harebrained collectively.
You can discuss the following things freely: money, sex, religion, family.
You hate all the same people, no questions asked.
You’re Facebook friends with each other’s parents, siblings, and significant others.
You can sense each other’s emotional state over text message, based on punctuation and Emoji usage.
You keep each other updated on your bodily functions. Maybe too vividly.
You’ve stopped feeling the need to wear pants around each other.
You reserve your most colorful and most vulgar insults for one another. | 22 Signs You've Found Your Best Friend Forever
You literally always owe each other money but trust that you’ll balance out over the years.