Shiva Purana
अनुह्रादश्च ह्रादश्च संह्रादश्चैव वीर्यवान् ॥ प्रह्रादश्चानुजस्तत्र विष्णुभक्तिविचारधीः॥ १८॥
They are Anuhrāda, Hrāda, Saṃhrāda and Prahlāda. The youngest Prahlāda was a devotee of Viṣṇu.
english translation
anuhrAdazca hrAdazca saMhrAdazcaiva vIryavAn ॥ prahrAdazcAnujastatra viSNubhaktivicAradhIH॥ 18॥
hk transliteration by Sanscript