Since I was a child, Francis has been one of my favorite saints.  That's probably not surprising since my middle name is Francis, but that is certainly not the only reason.
    He was born on September 26, 1181 or 1182.  His father was a wealthy merchant.  Not much is known about his mother but I think we can safely assume she was a religious person.  When he was born, his father was away on a business trip.  His mother named him Giovanni di Bernardone in honor of John the Baptist in hopes that he would grow to be a great religious leader (I have to wonder if she had any visions or dreams to give her that idea, but there is no record of such).  His father was not happy with the choice since he wanted his son to be a businessman like himself.  He changed it to Francesco.  
    There are differing opinions about how Francis behaved as a young man.  Some say he was a typical spoiled wealthy child, but others point out that he sometimes got in trouble with his friends and father for showing mercy and charity by giving goods away to beggars when he was supposed to be selling them. 
In 1204, a serious illness caused him to start taking a deeper look at his spiritual side.  In 1205, while visiting Spoleto, he had his first vision causing a deepening of his spiritual crisis.  Afterward, he gave up sports, feasting, and general frivolity with his friends.  He spent much of his time praying for enlightenment.  In the church of San Damiano near Assisi, he had his second vision or mystical epiphany.  He saw the crucified Christ come alive and say to him: "Francis, Francis, go and repair My house which, as you can see, is falling into ruins".   Originally, Francis took this to mean the church building he was in at the time, so he sold his horse and some cloth from his father's supply and gave the money to the priest.  His father was furious.  After much arguing and chastisement, Francis denounced his father and even took off the garments his father provided (we can imagine his father saying: "I've given you everything, even the clothes on your back.").  He returned to town living as a beggar himself and spent his time restoring some old churches.
In 1209, Francis heard a sermon based on Matthew 10:9, which caused him to go forth and began preaching repentance.  He was soon joined by others and within a year had eleven followers.  The original "Poor Friars" was born.  At the end of the year, Francis took his followers to Rome and obtained informal recognition of the group from Pope Innocent III and the title Deacon which formally gave him the right to preach the gospel.
    His new order grew quickly.  One of the new members was Clair of Assisi, who became Saint Clair and founder of the Poor Dame, later renamed the Poor Clair's , the female branch of the Franciscan order.
In 1213, the mountain of La Verna was given to the order by count Chiusi.  The mountain became Francis' favorite retreat for prayer (He is starting to sound like an Essene, who always climbed to a mountain top to say their morning prayers).  Francis wrote much poetry, his most famous is the Canticle of the Sun.
    In 1224, Francis had another vision, of a six-winged angel on a cross.  When the vision ended, Francis had stigmata.  The stigmata, and an eye disease, caused Francis to become progressively weaker.  He died in 1226 and was declared a saint in 1228.  
    Most of the above is from the official biographies of St Francis.  They leave some things unexplained.  We know of his love for animals, but it was more than that.  He referred to animals, flowers, trees, even the sun and moon as his sisters and brothers.  It is claimed that he could communicate with animals and was even known to preach to birds.  This sounds to me like more than a simple appreciation of nature.  It sounds to me like Francis could actually see, or at least sense, the spirits in other living things (and I include the sun and moon as living things)
and so recognized that they we're not so different than he was.  Again, this sounds very much like the Essenes, who did not like to kill animals and strongly opposed the animal sacrifices at the temple.
Francis may have not even known who the Essenes were, but they would certainly have welcomed him as one of their own.