Why did Ibrahim seek forgiveness for his father late in his life after Allah had forbidden him from doing so, and knowing that he was not blessed with a child until late in his life and thanked Allah for it?

Regarding the verse, there are sayings among the exegetes concerning Prophet Ibrahim's supplication for his parents. Among them are: that the supplication was made before their enmity towards Allah was confirmed; or that he sought forgiveness for them on condition of their embracing Islam; or that he meant Adam and Eve; or his two sons, Isma'il and Ishaq. The Quranic order does not necessarily indicate chronological order.