Gremory, Zeoticus

ジオティクス・グレモリー

Lord Gremory serves as the current head of the Gremory Clan of Devils. He is the father of Rias Gremory and Sirzechs Lucifer, as well as the grandfather of Millicas Gremory.
He appears as a middle-aged man with crimson red hair.
Hailing from the Gremory Clan, which is known for its extraordinary affection, Lord Gremory has shown a very kind disposition.
Little is known about Lord Gremory's past, other than the fact that he married Venelana Bael and eventually fathered two children: Sirzechs and Rias. When Sirzechs became the Satan, "Lucifer," and lost his right to become the Head of the Gremory Clan, Lord Gremory made an arrangement with the Phoenix Clan for his daughter to marry Riser Phoenix at some point before the series.
When the girls of the Occult Research Club are ordered to begin living with Issei, Rias asks her father to renovate Issei's house into a mansion. Although the house he designs features three floors, two basements, an underground pool, and a massive kitchen, the mansion he originally had in mind was to be much larger and staffed with many maids.
Lord Gremory seems to get along well with Issei's parents and even seems to take for granted that Issei will end up with Rias anyway, once calling Issei "Son."