User blog comment:B214/High School DxD EX/@comment-219.92.252.80-20160129063342/@comment-23853100-20160129074233

The mother is Ise. In the future due to overusing the DxD mode Ise became genderless and immortal, Ise in his drunk state has a one night stand with Sirzechs who is also drunk. The child between the two is Ernestine. Also because of this incident, Sirzechs became shock & depressed and end up committing suicide, Ise also tried to do so but because he's now immortal he can't so he place all his focus on work to prevent himself from thinking of that terrible night.