The only thing that I would change is to add the commas in the appropriate places and replace " the creation of familial difficulties" with "to create family difficulties."

Sibling confrontations arising from their deep -rooted hostilities against one another can create familial dificulties that can last for years. unrequited > not returned/one -sided as in unrequited love> not the correct choice of word From their relentless hostility against ../from theirmutual hatred for one another/from their mutual and reciprocal hostilities against ..> All ok. From the seeds of their mutual and deep-rooted hostility , confrontations between siblings can arise to cause familial difficuties that last for years

You try: "Sibling confrontations contain the seeds of unrequited hostility that can create familial difficulties lasting for years" Or perhaps more simply: "Unresolved sibling hostility can lead to family difficulties that last for years"