Who is Llewelyn Farr from The Reckoning and what is their importance?

Llewelyn Fawr is the grandfather of Llewelyn ap Gruffydd. He is loved by his grandson, but hated by Llewelyn's father and mother. Llewelyn's love for his grandfather places strain on his relationship with his parents. Llewelyn Fawr struggles to unite Wales and his grandson shares his idealistic vision of their homeland.