Whether or not you were kids, or it only happening once, isn’t what defines sexual abuse. Kids abuse other kids (COCSA, child on child sexual assault/ Child on child sexual abuse). Whether once or a thousand times? Doesn’t change what it is. (Consider eating a cheeseburger. Did you
really eat a cheeseburger, if you only ate 1? Or is there a specific number of times, or a specific number of burgers, that you have to eat before it counts as eating a cheeseburger?).
Nor does the fact that it was sexual make it abuse. The vast majority (read: nearly all) kids experiment sexually with each other. Most typically in 2 different Pre-puberty age groups; toddlers & early elementary. Toddlers via their own curiosity, elementary school kids vis shared curiosity / things they’ve learned about from other kids in school.
Yes. It could be sexual abuse.
Yes. It could be normal experimentation / kids being kids.
Yes. It could be 1 kid acting out their abuse + 1 kid experimenting
Regardless of whether it was sexual abuse or not? If it’s something that is causing problems in your life, or concerning you, it’s very much worth working with a therapist. People see therapists when absolutely nothing is wrong, they simply want to be a better person / the best version of themselves & hire an expert to help them get there... so whenever you’re asking yourself if something is “bad enough” to see a therapist? The answer is: it doesn’t have to be bad at all, much less bad enough.
You’ll also probably find this thread, & the links contained therein, helpful.
Sexual Assault - Are you wondering if you were raped? read this first.