For some reason, my head will match two bands together. It usually happens whenever they come out at the same time, and/or have a similar style. For example, I still pair Godsmack with Disturbed. I'm not exactly sure why my head does that. But I know exactly why I get Rival Sons and Glorious Sons confused.
According to Wikipedia, Rival Sons formed in 2009, and landed a record deal in 2010. Glorious Sons formed in 2011, and signed to their label in 2013. But somehow, they're both garnering attention at the same time.
While they are both played on the Mainstream Rock radio, after you listen to them for a while, you start to realize they have slightly different sounds - only slightly, though. I actually first heard Glorious Sons a couple years ago. A friend played me their song, "Heavy." Arguably, that's actually close to the sound of Rival Sons. So when I eventually heard Rival Sons, I was very easily confused. But now that "S.O.S" and "Panic Attack" have been released, I can hear a difference.
Rival Sons has a more bluesy sound. They're two singles, "Do You Worst" and "Keep on Swinging," remind me of Blues Rock band, The Black Keys. If you don't call either of them Blues, you can still admit they have a similar sound.
Glorious Sons has more of a rowdy style. They glorify drugs and the party lifestyle. Sure, they may have deeper meanings, but it's easy to pick up on the lyrics, "got me hooked on Oxycontin" in "S.O.S. (Sawed-Off Shotgun). Their other single, "Panic Attack," has slightly different subject matter, but the slacker anthem paired with the previous single give me Theory of a Deadman vibes.
Any case, I dig both these bands. And even though I'm starting to tell the difference, like Godsmack and Disturbed, I'll forever pair them together in my head.