User blog comment:B214/Volume 23 discussion blog/@comment-31137559-20170319155109/@comment-30924344-20170319161618

All humans who are reincarnated into whatever species can have children born with a Sacred Gear.

It's unknown if his spouse is human (or was if she died).

The Holy Sword Project simply just performed experiements on children to get them to wield any holy sword whereas the Sigurd Institution took the genetic codes of the original Siegfried and artifically created humans with that as the source, with many different genetics made later, to be able to make an artificial human who can wield Gram without dying from its curse. Freed and Lint were 'made' from the same genetics so they are artificial siblings to each other. They have not succeeded in making a human who can wield Gram.