Stevens was born on August 31, 1918, in Hawi, North Kohala, Hawaii. She was a descendant of Charles Stevens, an American whaler who arrived in Hawaii in the 1840s. She was born one of six children of Robert Naea Stevens and Julia Kaaoaolahilahiokeohokalole Bell. Her name Napua was a shortened version of her name Kawaiala Kao'ionapuaopi'ilani which means "the perfumed water" and "the finest flower in the bouquet of Pi'ilani. She was of Scots and Native Hawaiian ancestry and was a descendant of ancient Native Hawaiian kings.
