User blog comment:Theory of everything/Grimm Speculations Part Six: The Grimm Family Tree/@comment-206.211.150.253-20120905031323/@comment-1966944-20120906202638

We really don't know Renard's age. On the surface Renard looks to be in his mid to late forties. Nick appears to be in his late twenties. So there is enough of an age gap on the surface for Renard to be Nick's father and there is always the possibilty that Renard is much much older than he looks due to whatever he may turn out to be (Warlock?) or any potions or spells he may be under. His appearance may not have changed over the years and he may look the same today as he did decades ago. If he did indeed have a relationship with Kelly that resulted in the birth of Nick, Kelly may not have known nor cared what Renard's actual age really was.