Methuselah lived after he fathered Lamech 782 years and had other sons and daughters.
Concerning Methuselah observe, 1. The signification of his name, which some think was prophetical, his father Enoch being a prophet. Methuselah signifies, he dies, or there is a dart, or, a sending forth, namely, of the deluge, which came the very year that Methuselah died. If indeed his name was so intended and so explained, it was fair warning to a careless world, a long time before the judgment came.
Commenting on Genesis 5:25-27
Lamech--a different person from the one mentioned in the preceding chapter [Gen 4:18]. Like his namesake, however, he also spoke in numbers on occasion of the birth of Noah--that is, "rest" or "comfort" [Gen 5:29, Margin]. "The allusion is, undoubtedly, to the penal consequences of the fall in earthly toils and sufferings, and to the hope of a Deliverer, excited by the promise made to Eve.
Seth bore the image of God as Adam did, yet corrupted by sin transmitted through his father. The recurring refrain "and he died" announces death as an unchangeable law from Adam onward; yet each man fathered children before he fell, so life persisted amid death, and the race endured to bring forth the Seed who would conquer death itself.
AI summary
Commenting on Genesis 5:3-32