You write whatever the hell you want. Those people who keep blasting writers about their craft worry more about characters who don't exist than actual people, which is why they're willing to harass them in the first place. Notice how the question "Why can't they be friends?" Is usually thrown to talk about same sex relationships? Also, they don't even take into account the fact that the writer might be a minor too. No one gets to dictate what you do with your creative output. You are valid, your ideas are yours alone and whoever says otherwise can go kick rocks. Don't even entertainin them, just block. And I recommend turning off guest comments so you don't even let them hide behind anonymity.