Martin was born of John de Porres, a Spanish nobleman and knight of the Order of Alcantara, and a black free woman named Anna Velazquez. Martin’s father was not very happy to find that his child was black. He did not want to be connected with the child in any way. As a matter of fact, on the baptismal record, there is no mention of the father at all. The baptismal certificate only states "Martin, son of an unknown father". But some years later, he officially acknowledged Martin as being his son. We’re not sure if John ever married Anna Velazquez. If he did, he didn’t treat her very well. He spent most of his time in other countries, leaving Anna and the children, Martin and his sister Joan, to fend for themselves.

Though Martin was not from a poor background, you would not have known it by the way he and his family lived. They were always at least living in borderline poverty, and sometimes full-blown poverty. But none of this had any detrimental effect on Martin. Instead, it gave him an understanding and empathy for his poor brothers and sisters.

From his earliest days, he focused completely on God, being present in the tabernacle of all the churches of Lima and in helping out the poor. His mother became furious with him in the early days. She would send Martin shopping for food, entrusting to him with the meager pennies the family had, just enough to get some bread and a few necessities to see them through their days. Martin inevitably took the money and gave it to the poor. When he returned home with nothing in his basket, his mother would let him have it. "How can you give to the poor? We are the poor! It’s bad enough that you will not eat today, but what of your sister and me? We didn’t volunteer to starve!"

He got lost in the churches. This was his most favorite time. When he entered the dark, cool church, the entire world was left outside. He was in a haven. He spent hours before the Blessed Sacrament, before the crucifix looming high on the altar or a statue or painting of Our Lady. This was truly his home.