User blog comment:B214/Question and Answers 6/@comment-95.90.227.243-20160720132354/@comment-134.115.2.116-20160722125004

There is a fanfic where Issei is a grandson of a god, but he's not related to Shiva in your case. Check out 'Dragon Emperor of the Heavenly Storm' by dragonliege242 in fanfiction.net.