Well...
I was first exposed to the series when I was nine. We luckily were able to obtain the PS2 after the long haul from west coast to east coast.
Dad bought KH1 for reasons I will never know and said, "Here, bought it for you." I was weirded out because I remember before then of these big boss shadow-like creatures that ultimately scared me away from playing the whole game.
About a year later I got the dsi and wanted some games. We were at Sam's one day and I saw one game in particular that looked extremely familiar to me, 358/2 Days. I looked at it and asked her for the game. She bought it. I wimped out shortly after playing the missions due to the flying mammoth aerial BEASTS.
NOW IN 2015, I played some Witcher 3 and thought 'wow, rpgs are cool games why didn't I do this before." So I searched the web and a lightbulb click in my head.
"Hey, what about those games you chickened out in?"
LUCKILY ENOUGH, it was around E3 and the KH3 trailer was out. I pretty much gasped in amazement and went back to watch everything KH. Subsequently I cried for the next few days for Roxas's story.
Yeah. Not my proudest moment.
And that is how I got into the KH hell.