At first I (Oliver) thought that it was just me, and that I was fictionkin and an age regressor. But then I began to realize that when I was kinshifted or age regressed I didn't feel like myself anymore. After I made that realization it became really clear that I was never fictionkin or an age regressor -- that was our fictive and one of our littles. Because we share a unique mental connection it was really hard to figure it out, and I suspect that there was more than just me in the body for a long time. But to answer the question: I figured it out by learning about systems and looking closely at my 'different personalities' that turned out to be headmates.