No, he wouldn't. Siblings in the show don't have the same hair, even twins. The ONLY exception being the Flim Flam twins. And this picture does not have twins. Plus saying that's her older brother is so anti-parent.
Him being her older has an extreme lack of support, and for obvious reasons. Plus, it's anti-parent to call him her older brother since you haven't seen Rainbow's parents.
I'm going with brother... He looked about Armor or Big Mac's ages in their respective flashbacks... Hmmm, maybe more Armor's age than Big Mac's age... I call him Stratus...
Yeah, and Stratus looked young too... I won't deny it's possible he's her dad, but I won't dismiss the big brother possibility... At the very least not until it's confirmed or denied... My opinion is brother, but I won't put someone down for saying he's her father...