He met his wife, Bonita Morelli, on the Churchill Ferry in former New York where he dazzled her by talking about his favorite music, 1940s Jazz music, it's unknown how he learned about Jazz as it is considered rather dated. He has one son, Jersey Morelli.
Sometime in the past he worked with the A.I. Melissa. Melissa really liked Jason because he would play his jazz music for her to listen to. It was her who gave Jason the nickname, The Castaway. When Melissa was blown apart one of the reasons she chose Jersey's computer was because she remembered and liked Jersey's dad.
Presently he is attached to Naval Intelligence, Radio Beacon Deployment Program, and has been away from home for 513 days as of the date that Durga is found by Jersey Morelli. Jason avoided the Fall of Reach due to an assignment on the UNSC Silberg.
Though the exact date and cause is unknown, as of October 20, 2552, Jason Morelli is listed as a casualty of the war. His name is among a long list of others inside ONI Alpha Site, a Section 2 facility, in New Mombasa. It's possible this is just an Easter Egg reference to ILBs by Bungie, as other, less canonical and/or nonsensical names are also mentioned.
Partial transcript of Jersey.wavEdit
Durga: ...Give me a target.
Jersey: What's my name?
Durga: Jersey Morelli...
Durga: Father Jason is a Corporal in the Signal Corps attached to Naval intelligence, Radio beacon deployment program. He left you the material currently playing over this room's audio servers.
- Jason Morelli's rank is highly unusual, as Corporal is not a UNSC Navy rank. It's possible he was seconded from the Marine Corps.