Could the religious texts which say that the parents of the one who memorises the Qur’an will be given a crown of dignity to wear include his grandfather too?
Question

Will the grandparents of the one who memorises the Qur’an be given a crown to wear along with his parents?
Praise be to Allah.Ahmad (15645) and Abu Dawood (1241) narrated from Mu‘aadh ibn Anas al-Juhani (may Allah be pleased with him) that the Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever recites the Qur’an and acts in accordance with what it contains, his parents will be given two crowns to wear on the Day of Resurrection, the light of which is better than the light of the sun if it were in your houses, so how about the one who did this deed himself?”
This hadith was classed as da‘eef by Shaykh al-Albaani (may Allah have mercy on him), but it was classed as hasan by the commentators on al-Musnad (ar-Risaalah edition) because of corroborating evidence.
Ahmad (22950) narrated from Buraydah al-Aslami (may Allah be pleased with him) from the Prophet (blessings and peace of Allah be upon him) that he said regarding the companion of the Qur’an: “A crown of dignity will be placed on his head, and his parents will be clothed with two suits the value of which could not be estimated by all the people of this world. They will say: ‘For what have we been clothed with this?’ It will be said: ‘For your son’s learning of the Qur’an.’ Then it will be said to him: ‘Recite and ascend through the levels and chambers of Paradise.’ And he will continue to ascend so long as he recites, whether at a fast or slow pace.”
The commentators on al-Musnad (ar-Risaalah edition) said: Its isnaad is hasan, based on corroborating evidence, because of Basheer ibn al-Muhaajir al-Ghanawi, and the rest of its narrators are trustworthy (thiqaat), the men of the two shaykhs [al-Bukhaari and Muslim]. It was classed as hasan by al-Haafiz Ibn Katheer in his Tafseer (1/62), and some of its corroborating evidence is saheeh. End quote.
The apparent meaning of the hadiths quoted above indicates that this virtue will be attained only by the immediate parents of the person (his father and mother), because this is what springs to mind when hearing the word “parents.” Hence they are referred to in the dual [in Arabic]; if others were also included in that, they would surely be referred to in the plural.
And Allah knows best.