Hello and Happy Sunday!
What's to handle? This act was done, presumably a long time ago, and you're still ruminating over it? And what's the point in being coy about it? By injecting asterisks you meant to say, "oral sex," well, what of it? It happens among preteens and teenagers, whatever their relationship to each other, more than most people are willing to acknowledge, so join the club. It happened. It's over and done with.
You said, "older cousin." I can understand your coyness or even a bit of protectiveness with regard to your cousin, but the vagueness of your post doesn't help others with understanding it. What do you mean by "older?" Over 18, or merely older than the age you happened to be at the time? If you're hinting at this being a case of statutory rape, you'll have to be more specific before casting stones. Two underage teens having sex--one, perhaps, being slightly older than the other--does not fit the circumstance that statutory rape defines. If, on the other hand, you're wondering if oral sex between cousins, even if it doesn't involve actual penetration, still falls beneath the rubric of incest, well your suspicion would be correct. It is incest. But it's in the past; nothing was said or done to address the situation one way or another so what's the point of raking old coals that have long gone cold?
Let me make a suggestion: you said, "...but I didn't know any better?" Granted, but so what? What you're doing in effect is justifying an act that is still socially unacceptable. Okay. But you were hush-hush about it and now, it doesn't matter anymore. Let it go, for Pete's Sake.