Yosef was born on July 3, 1924 in Lublin, Poland, to Hannah and Fischel Numberg. His father worked in industry and his mother was a homemaker. His older brother was named Israel. Yosef studied in the Yavneh religious school. At nine, he joined Beitar in Lublin.
In 1935, he and his family made aliyah to Tel Aviv, where his father ran a company. Yosef studied in the Bilu religious school. In 1937, the family moved to Jerusalem, and he studied in the Tachkemoni School. Afterwards, he continued in the Alliance High School. He was active in nationalist circles, and in 1946, he joined Lehi in Jerusalem and was active in Department 6, in intelligence, and was trained with weapons and explosives. In the same year, the British arrested him on suspicion of being in the underground. He spent a number of months in the Kishleh in Jerusalem, until he was finally released.
Yosef returned to active duty with Lehi. In addition to his activity in Department 6, he participated in the battles of Lifta, Sheikh Badr, Der Yassin and Notre Dame. On 15 May 1948, he was injured by shrapnel.
After he recovered, he went back to active duty. In Camp Eldad and Camp Dror, he was responsible for all the new recruits. When HaMivrak, the Lehi newspaper, was founded, he was put in charge of it in Jerusalem.
His brother Israel, who also joined Lehi, was arrested after the Bernadotte assassination. He was imprisoned in Jaffa and Acre. Yosef managed to get out from Jerusalem to Tel Aviv.
After Lehi was disbanded, Yosef began working in textiles. To this day, he works in the importing of raw materials. Yosef was a member of the Herut Movement, then the Likud Party.
In 1962, he married Sarah Baltinester. They have two sons, Yair and Amikam, as well as grandchildren.