Sirzechs Lucifer/Relationships

Serafall Leviathan
Sirzechs seems to be on fairly good terms with Serafall Leviathan, not even reacting when she called him "Sirzechs-chan". This would imply that the two are relatively close to one another, as supported by Rias Gremory's statement that the Four Great Satans are very close to each other when they are in private.

Ajuka Beelzebub
Sirzechs and Ajuka have a long relationship with one another, having been close rivals since childhood. The two of them were the aces of the Anti-Satan Faction and both rose to become Satan after forcing the Old Satan Faction to retreat and were rivals even for the title of Lucifer. When Sirzechs was selected for the title of Lucifer, Ajuka accepted the title of Beelzebub. While Sirzechs relationship with Ajuka may seem to be bad due to the differences in ideology, their friendship is without a doubt a very close one, as Ajuka told Siegfried that the reason why he can concentrate on his hobbies is because of the fact that Sirzechs includes all of his will and further states that the only man he can call "friend" is Sirzechs.

Lord Gremory
Sirzechs shares a common father-son relationship with his father.

Venelana Gremory
Sirzechs shares a common mother-son relationship with his mother.

Rias Gremory
Rias is Sirzechs' younger sister and he cares a lot for her well-being. He even set up a match between Riser Phenex and Issei in order to help his sister prevent marrying Riser. When Rias was younger, Sirzechs and his father would take photos of her while she was sleeping.

Grayfia Lucifuge
Sizechs' wife. The two are deeply in love, and had a Romeo and Juliet style love affair (which fortunately ended much more happily). However, Grayfia often gets irritated by his laid-back attitude compared to her more serious and diligent personality.

Millicas Gremory
Sirzechs and his son have a good relationship with each other (mainly due to Sirzechs' childish attitude), playing together in their free time. Sirzechs even spent an entire night practicing the Satan Rangers pose with his son and was in shock and depressed when Millicas chose Oppai Dragon over Satan Red.

Surtr Second
Surtr is extremely loyal to Sirzechs after the latter rescued him from being terminated.

Issei Hyoudou
Issei has been in a good relationship with Sirzechs ever since he won the match against Riser. Sirzechs has faith in Issei's love for Rias and considers Issei as part of his family, even asking him on multiple occasions to call him his "big brother". He showed anger at Issei's death and, like the others, wanted to avenge him. He was also happy to hear his spirit was still alive.

Akeno Himejima
Sirzechs is shown to treat Akeno like his own sister, taking care of her well-being, even "arranging" that Akeno and the rest of the girls in the Occult Research Club to move in to the Hyoudou Residence, despite Rias' objection.

Yuuto Kiba
Sirzechs is shown to have a friendly relationship with Yuuto.

Koneko Toujou
Sirzechs was the one who rescued Koneko from being executed after Koneko's sister, Kuroka, killed her previous master and left her in Rias' care.

Azazel
Azazel is shown to be on friendly terms with Sirzechs after the alliance. The two of them are constantly seen discussing about Issei's future as well as his tokusatsu show, Oppai Dragon.