Valmiki Ramayana 7.111.22

पिता पितामहस्तस्य तथैव प्रपितामहः ।तत्पिता तत्पिता चैव विष्णुं यान्ति न संशयः॥

pitā pitāmahastasya tathaiva prapitāmahaḥ |tatpitā tatpitā caiva viṣṇuṃ yānti na saṃśayaḥ ||

Our plain-language meaning of this verse is waiting for scholar review.