Twin br.? of David Gruen

This may have been a twin brother of David Ben-Gurion:

From Wikipedia: "His father, Avigdor Grün, was a lawyer and a leader in the Hovevei Zion movement. His mother, Scheindel (Broitman), died when he was 11 years old. Ben-Gurion's birth certificate, when rediscovered in Poland in 2003, indicated that he had a twin brother who died shortly after birth."

https://en.wikipedia.org/wiki/David_Ben-Gurion

An article from Haaretz concerning David's brother:

https://www.haaretz.com/1.4706619