The stars mass (once it becomes a star) is inversely proportional to its lifetime as a main sequence star. A red dwarf can survive for many billions of years; a star that has twice the mass of the Sun, such as Sirius A, will have 25% of the Suns lifetime.
I believe when the mass of a star is bigger, it’s younger. When the star collapses on itself, it’s gravity pulls itself in. Creating a VERY dense star, which has less mass. Which means it’s older.
