Generations and generation of Buddhas

The Venerable Maudgalyayana put his faith in the Lotus Sutra, which is the greatest good there is, and thus not only did he himself attain Buddhahood, but his father and mother did so as well. And, amazing as it may seem, all the fathers and mothers of the preceding seven generations and the seven generations that followed, indeed, of countless lifetimes before and after, were able to become Buddhas.

The Writings of Nichiren Daishonin
On Offerings for Deceased Ancestors
Written to Jibu-bo Nichii's grandmother on July 13, 1279