A’lars, the guy with the Thanos chin, is a member of The Eternals who fathered the now infamous bad guy.
That said, The Eternals has been casting up and looks to be one of the next MCU movies to go into production.
Though, Thanos has some genetics from The Deviants buried within him as well, which could explain a lot.
If this thread would have stayed in the movie, we not only would have seen a young Thanos in the flesh, but we also would have seen him with several members of The Eternals.