You don't have to question it. And if you honestly know you would still love them if they had a looked completely messed up, were dirt poor, you would hold them when they had their worst crying fits, you wouldn't care any less about them for terrible flaws they had, if you would still love them, you're in love. You would die painfuIIy for them. Look up some medieval torchure (every time I say that word, my answer gets deleted). Or not. It's kinda scary. But if you would do any of those things for them, like instead of it happening to them, you really love them. You would never judge them for anything, or think less of them no matter what they do. You would rather be with them than anything else in the world. And yeah, trust me, if you loved someone, you would Know. Capital K.