(n.) Specifically, a grandfather; more generally, any ancestor.

C Father Time Methuselah Nestor Old Paar bicentenary bicentennial cental centare centenary centennial centennium centigram centimeter centipede centistere centred centref centrev centumvir centumvirate centurion century cwt dotard elder gaffer geezer golden-ager gramps grandfather grandsire graybeard gross hecatomb hundred hundredweight long hundred nonagenarian octogenarian old chap old codger old dog old duffer old geezer old gent old gentleman old man old party old-timer older oldster one C pantaloon patriarch presbyter senior citizen septuagenarian sesquicentenary sesquicentennial sexagenarian tercentenary tercentennial the quiet-voiced elders venerable sir veteran