The Thanos you refer to was how he was first introduced (along with Moondragon) in the mid-70s in the original Captain Marvel book (When he was male, pink, and used nega-bands)Thanos is a Titan. In the comics the Titans are a small colony of eternals living on Titan (Saturn's moon) and experimenting with whether Eternals can (and should) breed. Thanos is their fault/failure.
Movie Thanos clearly comes from a very large society which clearly didn't live on Saturn's moon. At this point, the Titans connection to the Eternals has been massively altered if not removed entirely. And we don't if Eros is trustworthy or literal in describing his link to Thanos.
