According to Thanos creator Jim Starlin, Avengers: Infinity War directors Joe and Anthony Russo cut 30 minutes of the Mad Titan's backstory from the film. At Las Vegas Comic Con, Starlin indicated fans could have gotten much more of the character's background on Titan had things played out differently.
Thanos' origin was touched on in the movie in order to build his ambition of population control across the galaxy. Other than this conquest and his love for his "daughter" Gamora, though, the details of his past were few and far between. According to Collider, Marvel Studios may add the footage into an extended cut of the film, maybe even to help celebrate its 10 year anniversary and Infinity War's monumental reception.
Given that what goes into an extended cut -- if there's one at all -- will be dictated by the directors and the studio and not Starlin himself, all this must be taken with a grain of salt. Of course, many fans would love to see more of Thanos growing discontent with his people on Titan. For now, those who want more of Thanos' upbringing will just have to fill in the blanks from Infinity War or possibly wait until Avengers 4, where we might get a deeper dive into the powerhouse villain during his formative years.
Now in theaters, Avengers: Infinity War is directed by Joe and Anthony Russo and stars Robert Downey Jr, Chris Evans, Chris Hemsworth, Scarlett Johansson, Mark Ruffalo, Paul Bettany, Don Cheadle, Anthony Mackie, Elizabeth Olsen, Chadwick Boseman, Benedict Cumberbatch, Tom Holland, Chris Pratt, Zoe Saldana, Bradley Cooper, Vin Diesel, Pom Klemtieff, Dave Bautista, Karen Gillan, Tom Hiddleston, and Josh Brolin.