Well, during Hyperspace war most of the sih species were somewhat mixed with jedis (humans and propably some other races too). Marka Ragnos was sith/human hybrid.
"Around 7,000 BBY, Dark Jedi exiles fleeing from the Galactic Republic after their defeat in the Hundred Year Darkness, established themselves as "divine" rulers over their native Sith, uniting the world once again, this time under the rulership of a Dark Lord of the Sith. Over the generations, the Sith interbred with the Human Dark Jedi through a practice of the intermixing of human and Sith bloodlines which became known as Sith Alchemy. Eventually, the Sith species in its original form was almost extinct."