Kazane is a Truly Single Parent
There is a suggestion of the Honoka and Kasumi having a father who has apparently separated from their mother (okay it was in a dream sequence but still) but there's not even a hint of something similar for Ayaka so far.- As of chapter 53, jossed.
Mikage-sensei is the Takamiya siblings father
Just to ensure that an apparent Muggle like Komachi would have children who have at least the potential to be witches. It's also why he's taking such an interest in Honoka. Kazane and Komachi will get back together at some point
Probably the moment Honoka and Ayaka get married.