The Darwin family was not "used" by the eugenics movement for their name, they FOUNDED the eugenics movement.
As for your assertion that the communists rejected Darwinism, that is completely unfounded. The ONLY people who try to say this are Darwinists.
The Communists rejected Darwinism and genetics in favor of a Lamarkian mechanism championed by Lysenko.
In the Soviet Union you could (and would) get sent to Siberia if you taught about genetics or Darwinian evolution.
My Molecular Genetics teacher was banned from teaching in Russia and was only allowed to immigrate into the USA via the intercession of Ronald Reagan.
So the ONLY people who say the Soviet Communists rejected Darwinian evolution are those with KNOWLEDGE.
Something you are evidently lacking...... in spades.