Does it matter which madhhab I follow when drafting a will?

He shares with them. The grandfather does not exclude full or consanguine brothers and sisters; he inherits alongside them, and is given whichever is better for him — dividing the residue with them as though he were one more brother (muqasama), or a guaranteed floor. With no other fixed-share heir present the floor is a third of the estate; so with one or two siblings he does better by sharing, and with three or more the third is worth more and he takes that. Ibn Qudama sets the Hanbali rule out from al-Khiraqi’s text, and adds that where fixed shares are also being paid the grandfather takes the best of three: sharing as a brother, a third of what is left, or a sixth of the whole estate — the Mawsu’a records that same three-way election expressly for the Shafi’is. The reasoning is that grandfather and brother both reach the deceased through the same father — the one is that father’s father, the other his son — so, as ‘Ali put it, they are two branches of one bough, each nearer to the other than to the trunk; and the siblings’ entitlement comes from Q 4:176, which no text cancels.

Sources: al-Mawsu’a al-Fiqhiyya, entry “Hajb” secs. 4–5 — “wa’khtalafu fima idha kana al-ikhwatu al-ashiqqa’u wa’l-ikhwatu li’l-abi yuhjabuna bi’l-jaddi abi al-ab”: Abu Hanifa holds the grandfather excludes them, reading kalala as not covering a case where a grandfather survives “li-annahu walidun li’l-mayyit”, with Abu Bakr al-Siddiq and Ibn ‘Abbas; “wa dhahaba jumhuru al-‘ulama’i wa humu al-Malikiyyatu wa al-Shafi‘iyyatu wa al-Hanabilatu wa sahiba Abi Hanifata ila anna al-jadda la yahjubu al-akha al-shaqiqa aw li-abin bal yarithu ma‘ah” (Ministry of Awqaf and Islamic Affairs, Kuwait) · al-Mawsu’a al-Fiqhiyya al-Kuwaytiyya, entry “Irth” sec. 30, al-jadd ma‘a al-ikhwa — “ittafaqa al-fuqaha’u ‘ala ‘adami tawrithi al-ikhwati aw al-akhawati li-ummin ma‘a al-jadd”; then, for full and consanguine siblings, “fa-inna al-a’immata: Malikan wa al-Shafi‘iyya wa Ahmada wa sahibay Abi Hanifata dhahabu ila tawrithi al-ikhwati al-ashiqqa’i aw li-abin ma‘a al-jadd. Wa dhahaba al-imamu Abu Hanifata ila anna al-jadda ya’khudhu hukma al-abi fa-yahjubu al-ikhwa”, with al-Tabari, al-Muzani and Abu Thawr agreeing with Abu Hanifa, and his two exceptions flagged forward to sec. 32 (Ministry of Awqaf and Islamic Affairs, Kuwait) · al-Mawsu’a al-Fiqhiyya, “Irth” sec. 31, nasib al-jadd ma‘a al-ikhwa — “lam yarid nassun fi’l-kitabi wa la fi’l-sunnati fi miqdari mirathi al-jaddi ma‘a al-ikhwa”; Zayd ibn Thabit’s doctrine, that the grandfather shares as a brother but never below a third, “wa hadha ma dhahaba ilayhi al-a’immatu: Malikun, wa Ahmadu bnu Hanbal, wa Abu Yusufa, wa Muhammadun min al-Hanafiyya, wa qayyada al-Shafi‘iyyatu dhalika bima idha lam yakun ma‘ahu sahibu fardin, fa-in kana ma‘ahu sahibu fardin fa-lahu khayru thalathati umur: imma al-muqasamatu, wa imma thuluthu al-baqi, wa imma thuluthu jami‘i al-mal”; and Ibn Qudama’s worked example for the Hanbalis (Ministry of Awqaf and Islamic Affairs, Kuwait) · al-Mughni, Bab mirath al-jadd cont. — the two camps named: with Abu Bakr (grandfather excludes) “Qatadatu, wa Ishaqu, wa Abu Thawrin … wa Abu Hanifata, wa al-Muzaniyyu…”; against them “wa kana ‘Aliyyu bnu Abi Talibin, wa’bnu Mas‘udin, wa Zaydu bnu Thabitin … yuwarrithunahum ma‘ahu wa la yahjubunahum bih. Wa bihi qala Malikun wa’l-Awza‘iyyu, wa al-Shafi‘iyyu, wa Abu Yusufa, wa Muhammadun”; with ‘Ali’s tree-and-branches image and Zayd’s valley-and-streams image (Ibn Qudama al-Maqdisi (d. 620 AH)) · Islamweb fatwa 66473, “Mirath al-jadd wa’l-jadda ma‘a al-ikhwa wa’l-akhawat” — “wa li’l-‘ulama’i minha maslakan: fa’l-Hanafiyyatu yunazziluna al-jadda manzilata al-abi fi hajbi al-ikhwati fa-la yarithuna ma‘ahu shay’an … wa’l-maslaku al-thani maslaku al-jumhuri wa minhumu al-a’immatu al-thalathatu Malikun wa al-Shafi‘iyyu wa Ahmadu”, with the three-way election worked on a real estate, and al-Rahbi’s line that uterine siblings are dropped by the grandfather (Fatwa Centre, Ministry of Awqaf and Islamic Affairs, Qatar) · al-Mughni, masa’il 4868–4869 — “wa madhhabu Abi ‘Abdi’llah [Ahmad ibn Hanbal] … fi’l-jaddi, qawlu Zaydi bni Thabit: wa idha kana ikhwatun wa akhawatun wa jaddun, qasamahum al-jaddu bi-manzilati akhin, hatta yakuna al-thuluthu khayran”; and, where fixed-share heirs are also present, the grandfather takes the best of three — sharing as a brother, a third of the remainder, or a sixth of the whole estate; plus the mu‘adda rule by which full siblings count the consanguine ones against him and then take what those receive (Ibn Qudama al-Maqdisi (d. 620 AH)) — every source in each list names that school at the page cited; the Mawsu’a’s “Hajb” entry names all three as schools (al-Malikiyya, al-Shafi‘iyya, al-Hanabila), and the Hanbali position is additionally taken from Ahmad’s own text in al-Mughni. The Mawsu’a notes one Shafi’i refinement — the third option, a sixth of the whole estate — which Ibn Qudama also gives for the Hanbalis; this pass did not find a Maliki source stating that third option, so the stance says only that all three share and guarantee a floor.

He excludes them. Abu Hanifa puts the grandfather in the father’s place: since a father indisputably shuts out the deceased’s brothers and sisters, so does a grandfather, and they take nothing. His grounds are that the Qur’an and the Sunna call a grandfather a father, that he already takes the father’s treatment in a long list of other rules, that everyone agrees a son’s son excludes siblings even though he stands at exactly the same remove from the deceased at the other end of the line, and that kalala — the condition on which siblings inherit at all — means an estate with no walid surviving, which a grandfather is. This was the ruling of Abu Bakr al-Siddiq, and of Ibn ‘Abbas and Ibn al-Zubayr among the Companions.

Sources: Islamweb fatwa 66473, “Mirath al-jadd wa’l-jadda ma‘a al-ikhwa wa’l-akhawat” — “wa li’l-‘ulama’i minha maslakan: fa’l-Hanafiyyatu yunazziluna al-jadda manzilata al-abi fi hajbi al-ikhwati fa-la yarithuna ma‘ahu shay’an … wa’l-maslaku al-thani maslaku al-jumhuri wa minhumu al-a’immatu al-thalathatu Malikun wa al-Shafi‘iyyu wa Ahmadu”, with the three-way election worked on a real estate, and al-Rahbi’s line that uterine siblings are dropped by the grandfather (Fatwa Centre, Ministry of Awqaf and Islamic Affairs, Qatar) · al-Mawsu’a al-Fiqhiyya, entry “Hajb” secs. 4–5 — “wa’khtalafu fima idha kana al-ikhwatu al-ashiqqa’u wa’l-ikhwatu li’l-abi yuhjabuna bi’l-jaddi abi al-ab”: Abu Hanifa holds the grandfather excludes them, reading kalala as not covering a case where a grandfather survives “li-annahu walidun li’l-mayyit”, with Abu Bakr al-Siddiq and Ibn ‘Abbas; “wa dhahaba jumhuru al-‘ulama’i wa humu al-Malikiyyatu wa al-Shafi‘iyyatu wa al-Hanabilatu wa sahiba Abi Hanifata ila anna al-jadda la yahjubu al-akha al-shaqiqa aw li-abin bal yarithu ma‘ah” (Ministry of Awqaf and Islamic Affairs, Kuwait) · al-Mawsu’a al-Fiqhiyya al-Kuwaytiyya, entry “Irth” sec. 30, al-jadd ma‘a al-ikhwa — “ittafaqa al-fuqaha’u ‘ala ‘adami tawrithi al-ikhwati aw al-akhawati li-ummin ma‘a al-jadd”; then, for full and consanguine siblings, “fa-inna al-a’immata: Malikan wa al-Shafi‘iyya wa Ahmada wa sahibay Abi Hanifata dhahabu ila tawrithi al-ikhwati al-ashiqqa’i aw li-abin ma‘a al-jadd. Wa dhahaba al-imamu Abu Hanifata ila anna al-jadda ya’khudhu hukma al-abi fa-yahjubu al-ikhwa”, with al-Tabari, al-Muzani and Abu Thawr agreeing with Abu Hanifa, and his two exceptions flagged forward to sec. 32 (Ministry of Awqaf and Islamic Affairs, Kuwait) · al-Mawsu’a al-Fiqhiyya, “Irth” secs. 47–48, the categories of residuary — the ordering puts the siblings after the grandfather “‘inda al-imami Abi Hanifata, khilafan li’l-sahibayn”, so that “dhahaba al-sahibani wa al-Hanabilatu ila anna jihati al-‘usubati sittun: al-bunuwwatu thumma al-ubuwwatu thumma al-jududatu ma‘a al-ukhuwwati…, wa ‘inda al-imami Abi Hanifata khamsu jihatin faqat” — the grandfather-with-siblings category being the one the Hanafi ordering does not have (Ministry of Awqaf and Islamic Affairs, Kuwait) · al-Mughni, Bab mirath al-jadd cont. — the two camps named: with Abu Bakr (grandfather excludes) “Qatadatu, wa Ishaqu, wa Abu Thawrin … wa Abu Hanifata, wa al-Muzaniyyu…”; against them “wa kana ‘Aliyyu bnu Abi Talibin, wa’bnu Mas‘udin, wa Zaydu bnu Thabitin … yuwarrithunahum ma‘ahu wa la yahjubunahum bih. Wa bihi qala Malikun wa’l-Awza‘iyyu, wa al-Shafi‘iyyu, wa Abu Yusufa, wa Muhammadun”; with ‘Ali’s tree-and-branches image and Zayd’s valley-and-streams image (Ibn Qudama al-Maqdisi (d. 620 AH)) — Abu Hanifa is named at every locus cited; Islamweb states the position of al-Hanafiyya as a school, and the Mawsu’a’s account of the Hanafi categories of residuary has no grandfather-with-siblings category “‘inda al-imam Abi Hanifa, khilafan li’l-sahibayn”. No source found in this pass records a later Hanafi fatwa-position against Abu Hanifa here — see the note.