Yassin was born in Omdurman in 1913. He joined the engineering department at Gordon Memorial College (today's University of Khartoum). He participated in the college in the first strike following the government's decision to implement a reduction in the salaries of graduates. He graduated in 1932 and was sent on a scholarship to the Military Survey School in the United Kingdom. He then worked in the Sudanese Survey Authority between 1933 and 1953.[2]
Yassin was elected a member of the Graduates' General Congress and was chosen as an assistant secretary and cultural secretary during the period between 1936 and 1943. He was also chosen as a member of the Preparatory Committee for the Graduates' General Congress in 1937.[2]
The First Sudanese Sovereignty Council ended on 17 November 1958 when General Ibrahim Abboud seized power in a military coup. Ibrahim Abboud assumed the presidency, and the council was dissolved, leading to a change in Sudan's governance structure from a parliamentary system to military rule.[10]
After the coup, Yassin chaired the Central Council Commission for the South which was tasked to look into the causes of the First Sudanese Civil War and the essence of the "South Sudan question"[11] in general, and suggest reforms.[12][13]