The possibility exists, although I don't think hornyness and restraint are things you inherit from parents you have never seen. But it is a fantasy world, so anything goes.
Although the number of half-siblings should be high for everyone. Assuming the male:female ratio was already the same two decades ago, everyone should have ~40 half siblings at average. Not that it matters who might be related with whom, when the r18 version has his whole family milking him legally (apparently).
