Nacho, 34, has left Real Madrid for the Saudi Pro League club this week.
His father, José María Fernández, told Radio Marca: "Nacho has explained it in a phenomenal way, he is aware of what he has meant for Real Madrid and he is in the hardest step of this decision: receiving all that affection.
"But it is HIS decision. As a father you know that we are there, but the decision is up to the children.
:"They (the children) have to feel safe, supported... and every time Nacho has made a decision it has been the right one . When he decided to stay it was hard, but he decided to stay at the club of his life... The only thing we can do is support them and not create doubts: think about it, meditate on it, take into account this in favour or this against.
"The feelings will change, because we have been living it for 20-odd years. We took him to the Sports City since before he had a driving license ... Changing his habit of going every day to Madrid, to Valdebebas, 15-20 minutes from his house... It is very hard, it is the club of his life, it is for everyone. But we see it with hope. It was a good decision, and it was at the best time."