well they arent 50% elf 50% human
they are human with some elf blood in their ancestry. Also in TES lore, when there is an actual couple of two different races, the child comes out as the mothers race
This, Say an Orc Male and a Redguard Female had a child, the child would be a Redguard. There was an example of this in Oblivion, cant remember his name but he was like Half Orc/Half Human (I want to say imperial, but not sure) his mother was an Orc, so he was an (Or more so) Orc.