IMAmImam Hasan's daughter was the mother of 5th IMAmImam of shia IMAmImam Mohammed Baqir a.s and IMAmImam Hussain's a.s son IMAmImam Zainul Abedin was his father.... So technically if you consider women as equal heirs 5th IMAm onwards all IMAmImam are descendants of both IMAmImam Hasan and IMAmImam Hussain