Board Thread:General Grimm Discussion/@comment-24.150.82.174-20150425033528/@comment-108.46.200.213-20170409070840

Kouf is saying that Kelly Nick's son is part of the blood-of-your-ancestors-and-strength-of-your-family thing which is  only referring to grimms (see below).

Marie and Kelly tell Nick in "The End" that "The strength of your blood, the blood of your Grimm ancestors" we can defeat evil.

http://www.springfieldspringfield.co.uk/view_episode_scripts.php?tv-show=grimm&episode=s06e13

KOUF:   But we also really wanted someone to tell us, “This is not a myth, a legend, or a fairy tale. This really happened.” And it seemed like the person to say that would be his son: “Because my father told me so.” And it also wrapped up the whole blood-of-your-ancestors-and-strength-of-your-family thing, as well.

MaryLikesGrimm