御祖父さん[ojiisan] grandfather
御父さん[otossan] father
異父[ifu] same mother, different father
家父長制[kafuchousei] patriarchal authority
外祖父[gaisofu] maternal grandfather

岳父[gakufu] (man's) father-in-law
杜父魚[tofugyo] sculpin (any fish of family Cottidae, inc. the bullheads and the miller's-thumb)
義父[gifu] father-in-law
教父[kyoufu] godfather
継父[keifu] stepfather

御爺さん[ojiisan] grandfather
老爺[shinpu] one's father
狸爺[tanukijijii] cunning old man
好々爺[koukouya] good-natured old man
爺が背[hizaragai] chiton (any marine mollusk of the class Polyplacophora)

エロ爺[erojijii] dirty old man
糞爺[kusojijii] old man
爺さん[jiisan] grandfather (may be used after name as honorific)
洞爺湖サミット[touyakosamitto] G8 Hokkaido Toyako Summit

御祖父さん[ojiisan] grandfather
御祖母さん[obaasan] grandmother
遠祖[enso] forefathers
開祖[kaiso] (sect) founder
外祖父[gaisofu] maternal grandfather

共同祖界[kyoudousokai] international settlement
教祖[kyouso] founder of a religious sect
元祖[ganso] originator
お高祖頭巾[okosozukin] kerchief worn by women in former times in Japan in cold weather, covering the whole head (except eyes)
始祖[shiso] founder