Answer
Medawar's father's nationality was Lebanese. His father, Yousuf Abul-Ahad, was a Lebanese Maronite Christian who immigrated to London as a teenager in the late 19th century. He became a successful businessman and married a British woman, Gertrude Medawar. Their son, Peter Medawar, was born in London in 1915 and grew up to be a renowned scientist.