Prior to the start of the series, he planned a engagement with Rias and Riser. Though after the engagement party was crashed by Issei, he reflected on his mistake of forcing his beliefs onto his daughter. It was revealed that he also had great love for his daughter when she was very young. He and Sirzechs would cry with joy and have nosebleeds by looking at how Rias acted when she was an infant, and took many video recordings of Rias.
He at first was disappointed at the fact Rias did not marry Riser to connect the families, but later accepted his daughter's content of loving Issei. He soon become fond of Issei and became good friends with Issei's parents and accepted him happily into his family, even wanting Issei to call him father. Like Sirzechs, he also shows great faith in Rias and Issei's relationship, although he often embarrasses the two (more often Rias). He also supports Issei's harem. After Issei proposed to Rias, Zeoticus tends to embarrass Issei by referring to him as "Rias's fiancé".
Gremory Clan Edit
Zeoticus's son. Zeoticus and Sirzechs has a close father and son bond, in fact their personality were very similar with each other in both kindness and refined mannerism and both father and son were also particularly doting on Rias, having work together to take video recordings of Rias in her childhood.
Venelana is Zeoticus's wife and the current lady of the Gremory Clan. She, like Zeoticus, was disappointed that the engagement between Rias and Riser Phenex had been broken off, but currently supports the love Rias and Issei show towards each other with great joy. While she loves her husband dearly, she is also very strict with him for acting silly, such as him dressing as Gomorin. Venelana when angered can make her husband fear her like Grayfia does with Sirzechs.