I always wondered how old the characters in the series are. I would assume that the use of prosthetics would get rid of signs of aging, so I have always been curious. I remember reading some where that Togusa was 27, but I have no clue about the others.
I've read that Kusanagi is in her early 40's. I'll assume that source is reliable for purposes of discussion.
I'm basing my opinions of Batou and Ishikawa on that assumption of Kusanagi's age, since they all three served together in the last World War. Batou is probably a few years younger, since he was a rookie in that episode. My guess for him would be 33-35. Ishikawa just seems to act a little older than she is, so I would say around 46.
My best guess would put Aramaki in his late 60's, since he's been asked in two episodes when he's going to retire. That indicates that he has already passed the typical retirement age.
As far as Boma goes, he's mentioned serving in the last World War as an explosives expert, so I would think he's close to the Batou's age, maybe a little older.
I have no clue as to Pazu's age, we're never given aany infor to go on as to his age.
Thing is with all of the cyberization of mankind, age matters little anymore. Especially humans with fully cyborg bodies. Aging is no longer a problem for them.
Just so you know, the flashback episode isn't a literal vision of what happened in the past. The whole point of the episode was that Saito was making it up, to put off his poker opponents, although there is probably a kernel of truth in it.
The reason I say this is because Batou didn't serve alongside the Major until the Nemuro Landing Operation, which happened in a separate conflict, years later. I'm actually pretty sure Batou was serving on the opposing side during the war in South America, as we see in his flashback episode in the first season.