Đaja married three times.
His first wife was French and she died young.
He married for the second time to Sofija Đaja, village teacher from Bavanište, Pančevo.
They had a daughter, Ivanka Đaja-Milanković (1934-2002).
Ivanka worked as a journalist in Sremska Mitrovica, where she died, though she spent a long time living in Canada.
Already at an advanced age, he married for the third time, to Leposava Marković (1910-1991).
She was his former student and collaborator and worked as an assistant and professor at the University of Belgrade.
They lived in Belgrade's neighborhood of Profesorska Kolonija.
Đaja was a good friend with Milutin Milanković.

His paternal uncle was Jovan Đaja (1846-1928), a journalist and politician, member of Nikola Pašić’s People's Radical Party.
He was president of Serbian association of journalists 1897-1899 and Minister of internal affairs of Serbia 1890-1891 and 1891-1892.
He was the one who invited Ivan's father Božidar to Belgrade, to helm the "Deligrad" ship.
Đaja married three times. His first wife was French and she died young. He married for the second time to Sofija Đaja, village teacher from Bavanište, Pančevo. They had a daughter, Ivanka Đaja-Milanković (1934-2002). Ivanka worked as a journalist in Sremska Mitrovica, where she died, though she spent a long time living in Canada. Already at an advanced age, he married for the third time, to Leposava Marković (1910-1991). She was his former student and collaborator and worked as an assistant and professor at the University of Belgrade. They lived in Belgrade's neighborhood of Profesorska Kolonija. Đaja was a good friend with Milutin Milanković.
His paternal uncle was Jovan Đaja (1846-1928), a journalist and politician, member of Nikola Pašić’s People's Radical Party. He was president of Serbian association of journalists 1897-1899 and Minister of internal affairs of Serbia 1890-1891 and 1891-1892. He was the one who invited Ivan's father Božidar to Belgrade, to helm the "Deligrad" ship.
Ivan Đaja