G-1: The Eagle - Ôwashi no Ken
Ken Washio
As Gatchaman, Ken is the leader of the team. To his knowledge, his fighter-pilot father was killed when he was four, and his mother died of illness when he was eleven. Adopted and raised by Dr. Nambu, at series start he delivers airmail with his little Cessna, lives in a shack next to his airstrip, and has a running tab at the Snack J that he never pays.
Though some fans have postulated that Ken is gay because he's either clueless or embarrassed when it comes to women, that's pretty weak evidence. Ken's problem actually seems to be that the one area he's not too smooth is romance—and let's face it, an 18-year-old who's spent most of his life training to be the leader of an elite ninja squad under a demanding mentor like Nambu probably hasn't had a lot of time or energy to be figuring out the dating scene.
Family
Midway through Gatchaman I, Ken learns that the leader of the Red Impulse team is in fact Kentaro Washio, his father—just in time to watch Kentaro climb into a rocket and blow himself up to stop a Galactor plan. Red Impulse faked his death when Ken was a child to become a spy for the ISO. In memories, Red Impulse pushes Ken to be strong, and in reality he'll accept nothing less, going so far as to give Ken at least one brutal beating when he believes Ken is being weak. 
(I'm the one who started RI "rat bastard" bashing years ago because what I see him doing to the child-Ken is physical abuse. Particularly because it's being done while father and child are playing, not as a form of "training" or in any other context that would make it less damaging to the child. I also think abandoning his child and wife and letting them both think he's dead...if that's his idea of honor, he should never have started a family in the first place.)
Though Joe has the reputation of being a rash rebel, Ken is at least as much of a troublemaker. Joe stands along the wall with his arms crossed looking moody; Ken argues. Wendy Dinsmore said it best: "Ken is the worst hell raiser and rebel on the team, but since he's the leader, he's used to getting his own way and always appearing right."¹ He makes plenty of bad decisions and runs off on his own more than once, often placing the entire team's lives in danger. And as the different series' progress and loved ones leave his life, he gets colder, harder, and angrier.
Battle of the Planets
Ken's "choir boy" persona can be blamed on the way Battle of the Planets' Mark behaved. The belief that there's a great deal of animosity and resentment between G-1 and G-2 came from the same place.
Part of the reason BotP's 7-Zark-7 is such a target for fan animosity is his sanctimonious monologues (ok, and that he's what was used to fill the time left by cut-back footage); Mark wasn't far behind him. Portrayed as a paragon of virtue, honor, and moral impeccability, he was contrasted with the "black sheep" of the G-Force family, Jason, whom Zark often pooh-poohed with a long-suffering sigh and a promise that all of Jason's problems were thanks to a bad attitude and imprudent behavior.
In both the Battle of the Planets cartoon and especially in the most recent comic books, a relationship between Mark and Princess was assumed. There's no real hint of this in the original Gatchaman series, though Jun did seem to develop an interest in Joe in Gatchaman II.
Voices for G-1
Gatchaman Mori Katsuji
ADV Gatchaman dubs Leraldo Anzaldua
Battle of the Planets Casey Kasem
G-Force Sam Fontana
Eagle Riders Richard Cansino
OVAs Onozaka Masaya
OVA English dubs Eddie Frierson
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References & Works Cited
¹ Dinsmore, W. Home of the White Shadow. http://www.chronicsite.com/gatchaman/comics.html