Half-Orcs are a combination of the races Human and Orc and did not start to appear until more recent history, as Orcs and Humans rarely got along enough to mate, and any offspring was seen as an abomination and promptly destroyed.
Half-Orcs are still prejudiced against to this day due to longstanding grudges between the races. They tend to not fit in with either race. They can be found anywhere Humans or Orcs can be.
Greater Half-Orc Families:
Note, due to their nature, no true fully Half-Orc families exist, this list includes Human and Orc families who are willing to acknowledge their combined offspring as heirs.