Shiva Purana
शिवो महेश्वरश्चैव रुद्रो विष्णुः पितामहः ॥ संसारवैद्यः सर्वज्ञः परमात्मेति मुख्यतः ॥ २३ ॥
Lord Śiva, Lord Maheśvara, Lord Rudra and Lord Viṣṇu are the grandfathers. He is the physician of the world and the omniscient Supreme Soul chiefly.
english translation
zivo mahezvarazcaiva rudro viSNuH pitAmahaH ॥ saMsAravaidyaH sarvajJaH paramAtmeti mukhyataH ॥ 23 ॥
hk transliteration by Sanscript