For the most part, the bodyguards are auto-generated when an heir matures.
I realize that, but the AI also seems to produce alot of those hatamoto units. I don't know what the support cost is for these, but I tinkered with the files and made them more expensive to produce and he still produced alot of them. I could have had them confused with heirs though. Does the AI get an easier job at marrying other clans princesses? I used to have a heck of a time getting my sons married! Even early in the game! Not to change the subject of course.