As far as I know all that is required is to make the appropriate bodyguard unit able to be recruited via a building. Whenever one is recruited, the game spawns the general that is part of the unit just like if he was being generated by some other way. At least, that's how it goes if I recall the discussions in the modding forum correctly.
Yup that's how you do it. They won't be part of the family tree but will be named characters.

One question though Lusted... Did you have to duplicate triggers with a different trigger condition in order to get the generals to come out with traits, or do they trigger one of the already-existing general creation events the vanilla game triggers use? Maybe they would count as coming of age? I certainly wouldn't think offered for adoption...
Haven't touched the triggers and new generals seem to come out fine.