Birth-name: Steven Jack McGarrett, Sr.
wife: Alexa McGarrett {Nee Alani}
Title: Ensign, and Unites States Navy Officer
Height: 6”10”
Status: Deceased
family: Doris Monroe-McGarrett (daughter-in-law; t), John McGarrett (biological-son), Debora McGarrett (biological-daughter), Steven Jack “Steve” McGarrett, Jr. (biological-grandson/doppelgänger), Tani Rey (biological-granddaughter/Alexa’s doppelgänger), Mary Ann McGarrett (biological-granddaughter), Joan McGarrett (great-granddaughter), and Alexa Alani-McGarrett (lawfully-married wife)
children: John McGarrett {1st-oldest son}, and Debora McGarrett {youngest-daughter}
Infiltration: United States Navy
Date-of-birth: July 30th, 1891
curremt-location: Pearl Harbor (USS Arizona)
In Season 4 Episode 10 -Ho'onani Makuakane (Honor Thy Father)- we learn that he would attend tutoring sessions with James Toriyama to prepare for an officer aptitude test. He was last seen by Mr Toriyama's youngest son, David Toriyama, on December 6, 1941 when he presented him with a gift for his father's help.
During season 7 episode 22 - Waimaka 'ele'ele - Steve learns that his grandfather went back down into the USS Arizona to flood the ammo shed so that the flames would not reach it during the bombing of Pearl Harbor. This allowed other sailors on the ship to make it off. Steve is unsure if anyone knew about this. Ensign McGarrett was awarded the purple heart posthumously.
In Season 9, episode Pua a'e la ka uwahi o ka moe we meet Steves grandfathers best friend Milton Cooper (retired HPD detective) and learn that his grandfather wanted to become a police detective. Milton gives Steve his grandfather attache case which has a old case file in it and repeatedly notes how much Steve looks like his grandfather.