Кертту was born in 1901. Кертту's father was Вернер Клеметтинен and her mother was Алма Муукконен. Her paternal grandfather was Адам Клеметтинен and her paternal grandmother is Мария. She had two brothers and two sisters, named Еэро, Урхо, Эстери and Эльза. She was the oldest of the five children. She died at the age of 77 in 1978.