The best (and most romantic) way of describing Johnlock. From my 86 year old Grandpa
Grandpa: You know, I think Sherlock and John might end up together.
Gramma: You think they're homosexual?
Gramma: So what do you mean you think they'll end up together?
Grandpa: (frustrated) I think that they're perfect for each other! I mean, just look at them together!
Gramma: (raises an eyebrow)
Grandpa: Stop with the homosexual! They should be with each other because they GO together! They make each other happy! Isn't that what being in a good relationship's about?
Grandpa: Saying someone's homosexual is like saying I love blonds.
Gramma: You do like blonds dear.
Grandpa: But you're not blond.
Grandpa: You never have been! I feel in love with you with brown hair and stayed in love when you turned grey. I love you for you. Grey or brunette, young or old. Just like John and Sherlock.
Grandpa: John may like women like I like blonds, but that doesn't mean he's going to ignore someone perfect for him just because it's not a woman. And Sherlock clearly loves him.
Gramma: I thought you said he's not interested in any of that.
Grandpa: Maybe not in other people. But look how he looks at John! He looks at him like I looked at you on our wedding day. It's love. Not something so trivial as whether he's a man or woman.
Gramma: I knew I married you for a reason.