User blog comment:B214/Question and Answers 2/@comment-3965848-20140228143236

Issei's parents don't seem to mind that so many girls are around thier son especialy how close. His dad was happy for him having a harem and even his mom aloud Rias and Asia to wear aprons while naked saying "it's like you have two wives". (probably out of desperation from wanting grandkids since he was unpopuler with girls.)

So how do you think they would react if they found out that thier son and his friends are not humans. I think naturaly that they would be shocked at first but after living together for some time they probably wouldn't mind (for as long as they have grandkids in the end.) XD