He's been in every nativity play this Christmas, but what do we really know about Joseph? We actually have no recorded words for him in Scripture, but in his case I believe his actions speak louder than his words and have so much to teach us.

Joseph offers an incredible example for those who choose to show grace and affection to children in need. I know I'm biased and we need to always be careful of reading into scripture what we want to see (isogesis) instead of reading out of it what God wants us to hear (exegesis). But I for one, want to claim Joseph as the patron saint of foster carers, adopters and stepfathers. Here are five reasons.

1. Joseph is not the biological father

"I could never love someone that wasn't biologically my own." I have heard this response so many times after I have given a talk on becoming a foster carer that I have to feign sympathy. I also bite my tongue to refrain from sarcasm - most of the men responding this way I know to have a deep passion and commitment to their dog, their car, their football team. And don't they know they have no biological connection with their wives? It's a crazy objection. Joseph models for us at the heart of the Christmas story that biology is not the determining factor for who we love.

Matthew's Gospel couldn't be clearer that Joseph was not the biological father of Jesus. It would have been a lot simpler if Jesus had been born from the sexual union of Mary and Joseph, as we wouldn't need the unprecedented claim that Jesus was conceived by the Holy Spirit.

The doctrine of the virgin birth has led to all sorts of confusion, including some who wrongly conclude that Christianity claims that God had intercourse with a woman. There are other miraculous births in the Bible: Isaac, Samuel, Samson, John the Baptist. All of them involve infertile couples becoming pregnant after sexual intercourse. But the New Testament claims that Jesus' was a virgin birth, a striking way of underlining that in a totally unique way Jesus was the Son of God.

But where does that leave Joseph? After being told by Mary that her pregnancy is due to divine interaction, the naturally sceptical Joseph needs his own divine encounter to be convinced to take Mary home as his wife and so begins Joseph's role as a father to someone else's child. Joseph becomes a foster dad before he has met the child to be entrusted to his care, and before he has even fully married his wife.

2. Joseph accepts Jesus as his son

When my foster children have been playing up in a shop, or causing chaos at school I must admit that on rare occasions I am tempted to turn to all the scornful observers and say "He's not really one of mine you know." Of course, I would never voice that - the children in our care have had enough betrayal and rejection in their lives. As a foster dad I take responsibility for the actions of these children because they have been the victims of so many terrible things - their behaviour is totally understandable once you know their stories. Whatever shame they may carry I choose to share that through association with them as their father.

I can only imagine what scorn Joseph must have faced when before the wedding his wife was pregnant. In the ancient world these things were taken very seriously but Joseph did not make a fuss. Rather he publicly identified with Jesus, accepting him as his son.

We know that many people around Nazareth identified Jesus as "Joseph's son" (Luke 4:22; John 1:45 and 6:42). Matthew's Gospel goes further - including Joseph's genealogy as Jesus', just as in our day adopted children are included into the new family tree as well as into their new family.

Joseph and indeed Mary and later Jesus' younger siblings too, welcomed this child into their lives as a permanent member of their family, irrespective of how he had come into their care. They loved him as their own.

3. Joseph wasn't in it for the money

I have heard of some fostering agencies enticing foster carers into the work with the promise of financial reward. But the reality is most foster carers do not get paid enough to cover the costs and there are far easier ways to earn money than bringing a looked-after child into your family. Yet I have found fostering to be one of the most rewarding things you can do - emotionally and spiritually. We have a clue about Joseph's financial position through a little incident in Jerusalem:

"Joseph and Mary took him to Jerusalem to present him to the Lord (as it is written in the Law of the Lord, "Every firstborn male is to be consecrated to the Lord"), and to offer a sacrifice in keeping with what is said in the Law of the Lord: "a pair of doves or two young pigeons." Luke 2:21-23

The ornithological offerings were not the usual sacrifices for someone the Bible describes as being of royal descent. Pigeons were not an ordinary sacrificial animal but were a concession for the poor. Joseph was not a wealthy man and taking on responsibility for Jesus did not increase his wealth - indeed as we shall see it caused him even greater hardship and struggle. Despite the financial challenges, and the increased instability of looking after Jesus, Joseph was committed to his son.

4. Joseph will go to any lengths to keep Jesus safe

Although some foster carers may go into the job with the idea that they are basically providing a bed and breakfast service for children, it will quickly become clear that caring for vulnerable children is much more than that, it's a whole way of life. It's far more than a hobby, a job or a responsibility.

Many adopters and carers I know talk about that fierce protective urge that begins from the moment of the first phonecall describing the predicament of a child or sibling group. It's an urge that takes their care far and above the call of duty and Joseph models this profoundly.

When King Herod was on the war path following the visit of the wise men to pay homage to a 'new King' he launches a murderous campaign to kill all the boys born in the region over the last two years. Joseph has an opportunity now. He could have abandoned Jesus, and returned to his original plans of marriage and biological children in due course. But Joseph takes full responsibility for Jesus, and that means he will stop at nothing to protect him even if it means relocating his work, his life and his family to Egypt. Joseph chooses to become a refugee in order to protect his foster son Jesus from harm.

5. Joseph wasn't perfect

With this picture of a protective, caring, committed and sacrificial Joseph, perhaps we may feel we are not good enough to be foster carers.

Especially if we are already parents and regularly struggling. If we are not careful foster carers are attributed some kind of superhero status that actually stops a lot of people from thinking about stepping forward to be the parents that children in the care system desperately need.

I wish I had space to write about the myriad ways I have failed as a parent. The stupid mistakes, the bad reactions, the wrong decisions and the diary clashes would be enough to convince you that our family is far from perfect. But Joseph can step in and help me out here.

Mary and Joseph have been given the most amazing privilege and incredible responsibility to raise God's Son as their own. But the last recorded interaction that the Bible has with Joseph involves a visit to the Temple in Jerusalem for Passover.

On their way home Mary and Joseph manage to lose the 12-year-old Jesus for three days. I have had the heart-attack-inducing feeling of losing a child for 10 minutes once and that felt like an eternity, so I can only imagine what it would feel like to have misplaced the Son of God for 72 hours. Strangely, I take huge comfort from this incident. God trusted Joseph to care for his son but he didn't expect perfection.

This is the last we hear of Joseph and the last and only recorded words we have of Jesus to his father are: "Why were you searching for me? Didn't you know I had to be in my Father's house?" These are tough words for a Dad to hear - talk of another father from your 12-year-old. I can't imagine how I will feel if my adopted daughter one day tells me she is meeting her "real dad." Somehow Joseph doesn't object to Jesus' words. Perhaps he knew his job was to point and entrust Jesus to his heavenly father.

So to all of you out there who remember painfully being cast as a shepherd, donkey or innkeeper in the school play and missing out on playing Joseph - well here's your chance.

Would you consider playing the role of Joseph now in the life of a child in need? Could you care for someone else's child? Could you through your actions rather than your words, point a child to a father who wants to adopt them into His family?

Dr Krish Kandiah is President of London School of Theology and founder of Home for Good, a fostering and adoption charity.