Ermengol married before 1048 Adelaide, whose family is not known, even if some scholars made her daughter of Guillem I Count of Besalu. She died before May 1055, leaving a daughter:

Isabel (died circa 1071), married Sancho Ramírez in 1065

before May 7, 1055, Ermengol took as his second wife Clemencia, presumably daughter of Berengar Raymond I and his second wife Guisla (this is hypothesized from the name of their 4 sons), by whom he had:

Ermengol IV, his heir

Berenguer

Guillem

Ramon

Clemencia died after June 26, 1057, and before November 6, 1062.