It’s great that all these characters have well fleshed-out backstories from the comics.
That’s a gold-mine for a good writer but should only be shown if it’s relevant to the story.
In the case of Johnny and Sue, their backstory is important because it means Sue had to take care of Johnny, and she’s not just his sister, but his mother as well.
If I were writing, I’d keep that in mind when writing scenes between Johnny and Sue.
She should be over-protective and bordering on overbearing at times, and he should be rebellious and sick of her always telling him what to do - while also being closer to her and truly loving her in a deeper way than most brothers and sisters.