"Maybe we should just stay here, Harry. Grow old."
Sometime ago I had learnt that a soulmate doesn't only have to be a romantic partner. It could be anyone — a friend, a family member, or even a random person. They were that for each other. Harry and Hermoine were each other's soulmate. They have always been there for each other, always trusted each other, always supported and helped each other, always cared and worried for each other. They had each other's back. They could share their feelings, hug, cry on each other's shoulders. They knew what the other one is feeling without having to say anything.
Now when I say that I ship them, it doesn't exactly mean that I am trying to force their relationship. It was never even implied that they can be a couple, but what I mean is that if two out of the three — Harry, Ron and Hermoine — had to be a couple, Harry and Hermoine would have been a far more better couple. I love Ron so much but, yeah.