[@MiddleEarthRoze] From the Dragon Age Wiki: "Children between dwarves and humans are extremely rare because of the low fertility rate of dwarves in addition to the small chances of producing offspring with other races. Half-dwarves are shorter than humans but taller than dwarves. Furthermore, it is more often that such mating would happen with surface dwarves as such union would be heavily stigmatized in Orzammar."

So there ya go! Rare, but possible.