Millions

Millions tells the story of 9-year-old Damian, a Catholic school boy, whose family moves to the suburbs of Widnes after the death of his mother. Soon after the move, Damian's "hermitage" in a cardboard box by the train tracks is disturbed by a bag of money flung from a passing train. Damian immediately shows the money to his brother, Anthony, and the two begin thinking of what to do with it. Anthony wants the money all to himself. Damian, kind-hearted and religious, had recently overheard three Latter-day Saint missionaries lecture other members of the community on building foundations of rock rather than foundations of sand, an old Christian principle which dictates that self-worth should be based on the teachings of Jesus Christ rather than any other object of worship such as Money/Mammon or Power. The lecture inspires Damian, who looks for ways to give his share of the money to the poor; at one point he even stuffs a bundle of cash through the missionaries' letter box, having heard about their modest lifestyle and deciding that they too must be poor.
Throughout the story, Damian commits small acts of kindness like buying birds from pet stores and setting them free and taking beggars to Pizza Hut, while Anthony bribes other kids at school into being his transportation and bodyguards, and looks into investing the money in real estate.
The story takes place in the weeks leading up to The Bank of England's (fictional) change from the pound (Â£) to the euro (â¬)- an event publicised as 'â¬ Day'. An assembly is held at Damian's school to inform the children about the change, as well as to educate the children about helping the poor. Realizing that the money, which is in pounds, will be no good after a few days, Damian decides that the best thing to do would be to give it away before the conversion. He drops Â£1,000 into the donation can at the assembly. The woman collecting the money, Dorothy, is forced to report Damian; when questioned by the principal, Anthony lies that he and Damian stole the money from the Mormons. Damian and Anthony are grounded that night. When their father collects them from school he chats with Dorothy, and there is an obvious attraction between them.
After the donation, Anthony's friend informs them that a train carrying notes which were to be destroyed after the conversion had been robbed. One bag was stolen in a diversion, while the robber remained on the train disguised as one of the emergency staff, and the money had been dispersed by throwing it off of the train at various locations throughout the country to be collected by the robbers. The boys logically conclude that their money was stolen, and Damian, who thought the money was from God, feels terrible.
Around this time, a mysterious man comes snooping around the train tracks and asks Damian if he has any money. Damian thinks that the man is a beggar and tells him he has 'loads of money'. However, Anthony realises he is one of the robbers, and gives the man a jar full of coins to cover Damian's tracks.
The robber eventually finds out where Damian lives and ransacks his house. Damian had informed his father about the money just before they came home to their destroyed house. The robbery is then explained. The robbers boarded the train. They then escaped the police by dressing as football fans and joining a crowd of similarly dressed fans leaving a game. However, one man remained on the train. He began to throw the money off, to be collected later. The robber who came sneaking around hid in Damian's room after ransacking it, much in the way the train robbery was carried out. Damian's father, who had resolved to give the money back, decided that if the robbers were going to steal his family's Christmas, then he would steal the robbers' money. The family, as well as Dorothy, go on a massive shopping spree on Christmas Eve.
That night, after they are asleep, their house is bombarded by beggars and charities begging for contributions, and seeing the confusion that results, Damian runs off to the train tracks to burn the money, deciding that it was doing more harm than good. While he is burning the money, he is visited by his dead mother, who tells him not to worry about her.
In the final scene, the audience sees Damian's dream of the family flying a rocket ship to Africa and helping develop water wells, while Damian narrates over the scene that each family member but him had hidden a little bit of the money beforehand. Damian convinced them to spend this money on the wells he is dreaming about. Earlier in the movie this was shown to be the most crucial and cheapest way to drastically improve the quality of life for many African communities.

Question: What had Damian's family members hidden?
Answer: Money