Before Garp revealed who Luffy's father was, I thought he was the son of the Pirate King and didn't know it.
Then Oda proved me wrong and gave Luffy a father I didn't know anything about, and it was quite disappointing.
But when I discovered Ace was actually Roger's son, I felt like he was supposed to be the main character of the series! I fell in love with him, soon to discover he died not too many episodes later (I still didn't read the manga back then). I was broken hearted, it was hard, and I couldn't stop thinking about him and making up all kinds of ways for him to still live. I wrote a fanfic with ongoing chapters at least once a week for about two years. It was about how I saved him and took him to the real world, where he underwend surgery in a hospital and healed from his wounds. He couldn't go back since it was the time-skip, so he took me by yacht on a journey to Japan, to ask Oda to return him to the story. I was in love with him for 6 years. But over the years, I grew way older than him, and he remained 20. Eventually I couldn't dream about him anymore, and my heart became open to accept a new love. There will always be a warm place in my heart for Ace, even if I think of King all the time now. I still carry his name in my username and I have no intention of ever changing it.