This is a really good article from the National Catholic Register.
The apparition at Fatima on Oct. 13, 1917, is the only approved apparition in 2,000 years in which the entire Holy Family of Jesus, Mary and Joseph appeared at the same time. The three little shepherd children saw Our Lady with St. Joseph and the Child Jesus, both blessing the world, during the time tens of thousands of people were witnessing the sun miracle.
The Miracle of the Sun was one of the most spectacular miracles recorded in the history of the Church. It was heaven’s verification of the message that the Mother of God came to deliver to the world. A miracle had been foretold months in advance, as to its exact day and hour. While the nature of the miracle was not foretold, three things were foretold: “In October, I will tell you  who I am and  what I want, and  I will perform a miracle so that all may believe” (July 13, 1917).
It is not correct to say that Our Lady foretold the Miracle of the Sun. She simply foretold a miracle, without stating what kind. The miracles of Jesus in the New Testament were to bring people to faith with a response in love. Such, too, was the reason for the Holy Family miracle of Fatima.
Before the release of the third part of the Fatima secret in 2000, Pope St. John Paul II sent two Vatican representatives to Sister Lucia. She took that opportunity to tell them that she had written a book. She requested permission from Pope John Paul to have it published. That book is described as having a catechetical dimension — and in fact is a “catechism of Fatima,” in both senses of the word. In English, it is titled Calls From the Messages of Fatima. In the preface, we read: “The entire message of Fatima is a great call to holiness for the Church of our time.
“Lucia sees this call to holiness in some of the details of the apparition. The presence of St. Joseph in one of apparitions is a pressing invitation to the sanctification of the family, a key theme throughout Lucia’s book and also one of the essential currents and main preconditions of the magisterium of John Paul II.”
Sister Lucia entitled the 18th chapter of her book “The Call to the Sanctification of the Family.”
Most importantly, Fatima is for faith, hope and love — and Fatima’s message can help the family to live in holiness, professing the totality of true faith.
Retrieved may 13, 2015 from http://www.ncregister.com/daily-news/fatima-is-for-the-holiness-of-families/