I really like the idea of both Robins as twins. I mean, it'd then include
getting annoyed with his brother being such a bookworm or other kind of a loser and is the active one of the two, but really loves his bro and tries to be protective or toting sibling to him.
Meanwhile
tends to tease her time to time or just provide her happiness because he's such a nice guy, but also thinks more before acting and has to be the wise self-control to his sister. Heck, this is how I'd wanna write both as now and then.
They feel such neat opposites in means of temper which I think would work on both being twins. So cute...
I'm not keen on selfcest-styled Robin x Robin unless it's more established both are more of different than same person. I'd call that more of Robin x Reflet.
Ok, has no one gotten the reference I put under my location? Someone's got to get it...
It's those things that you will see, get a laugh, and then resume whatever you were doing.