It is reported from Sayyiduna Ali (may Allah be pleased with him) concerning a husband and parents: for the husband a half, for the mother a third, and for the father a sixth.
Al-Hasan bin Umarah is matruk (abandoned), and it has been narrated through another route that is munqati' (broken).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الفرائض / 12303