Ubayd bin Nadlah said that Sayyiduna Ali bin Abi Talib (may Allah be pleased with him) used to give the grandfather a third, then he began giving a sixth; and Abdullah (may Allah be pleased with him) used to give a sixth at first, then he came to a third.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12436