Personally, I found they did a pretty good job in establishing the characters on both sides in Fates. The siblings were all interesting and likeable from the start and I was interested in learning about both sides. When Fates was revealed I already decided to do Birthright because of the setting and scenario of that game, but once I played it and got to that point, I felt bad making a decision. I really didn't want to join either side because I liked both sides, not the rulers mind you.
One of the problems in Fates is King Garon (who you mentioned), who is too much of a typical villain, as well as the whole story scenario in Conquest just... not working at all. There are other issues with Fates as well, such as some story bits falling flat and just not even making sense, but strangely, making the choice in chap 6 was not one of them I had. The characters clicked really fast with me and making that decision hurt more and more as each game delved further and further.
Dance my pretties!
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