Somen's family emigrated to Kenya in the early part of the twentieth century and was among those that established successful businesses in the country. Somen, who was also a one time president of the Board of Kenya Jews, lived in Kenya for over 30 years. His wife Sophie was born in Kenya. He was elected mayor of Nairobi in 1955 together with deputy mayor Dobbs Johnson.
Somen played a role in establishing amicable relations between Kenya and Israel. He returned to Israel from Kenya, though some of his family and relations still live in Kenya.