User blog comment:Bennia Lover/Age of Characters/@comment-185.112.105.215-20170509091936/@comment-1359322-20170509122336

"“Nhoho! It’s been a while♪ Uncle Azazel, looks like you are doing fine, hmm?”"

- Volume 16

"“In the end, Vali-kyun couldn’t endure his dad’s treatment towards him so he ran away from home~♪ I hear that you were raised by Azazel-kun at the Grigori~. I’m so happy for you, since uncle Azazel is good at looking after people~.”"

- Volume 16

So no Rizevim is younger than Azazel.