It can be prayed for one or both the parents, and the Thawab for this kind of kindness is immense.
NAMAAZ FOR ONE’S PARENTS (Waaledain includes grand PARENTS)
This Namaaz consists of 2 Rakaats. The Niyyat should be: “I am offering 2 Rakaat Namaaz-e-Hadiya Walidain, Qurbatan ilallah”. In the 1st Rakaat after the recitation of Suratul Hamd, recite with raised hands as in Qunoot the Dua given below, 10 times.
“Rabbanaghfirlee waliwa lidayya walil mo’mineena yauma yaqoomul hisaab” (14:41)
“Our Lord! Cover us with Thy forgiveness, me my parents and all believers on the day that the reckoning will be established.”
After this complete the 1st Rakaat with Rukuu and Sajdah and stand up for the 2nd Rakaat.
In the 2nd Rakaat after the recitation of Suratul Hamd, recite with raised hands as in Qunoot the Dua given below, 10 times.
“Rabbigh firlee waliwa lidayya walimun dakhala bayti mo’mineenun walil mo’mineena wal mo’minaat” (71:28)
“Our Lord! Forgive me and my parents and those who enter my house with belief and men who believe and women who believe.”
After this complete the 2nd Rakaat and Namaaz is complete. Then go into Sajdah and recite the Dua given below, 10 times.
“Rabbir ham huma kama rabba yani saghira” (17:24)"
“Our Lord! Forgive them both for they have brought me up in my childhood.”