The condition which Isaac's family had to establish was the foundation of substance, and this remained for his own two sons, Esau and Jacob to establish successfully.
God's activities with Jacob's family, from external appearance according to Scripture, raise many questions. Why did the twins Esau and Jacob fight even while in their mother's womb? (Gen. 25:22-23). Why was Jacob born with one hand grasping Esau's ankles (Gen. 25:26). Why did Jacob take the birthright from his brother? (Gen. 25:32-34). Why did Jacob cleverly deceive his blind father to gain his blessing? (Gen. 27:18-19). And why did God so love and protect Jacob throughout his life?