Shiva Purana
प्रपितामहनामा च सपत्नीकाः प्रकीर्त्तिताः ॥ मातामहात्मकश्राद्धे त्रयो मातामहादयः ॥ ४२ ॥
They are also mentioned as having co-wives by the name of their great-grandfather. In the shraddha consisting of grandparents there are three grandparents.
english translation
prapitAmahanAmA ca sapatnIkAH prakIrttitAH ॥ mAtAmahAtmakazrAddhe trayo mAtAmahAdayaH ॥ 42 ॥
hk transliteration by Sanscript