An artist at play: the unseen side of Picasso

When Pablo Picasso presented an ornate, cut-out doll to the four-year-old daughter of his close friends as a birthday gift, the girl promptly burst into tears because she had wanted a doll she had seen in a toy shop, not a creation from the Spanish artist's own hand.

Lucia, the daughter of the Italian model and actress, Lucia Bose, and the star matador, Luis Miguel Dominguin, could never have known Picasso's gifts of drawings, cut-outs and prints which he created for her and her two siblings, would come to be the family's most remarkable possessions.

The 40 artworks, many of which were inspired by the three children, their parents and Spanish nanny, have since been credited with shedding a unique light on the artist's playful side as well as his love of children.

The collection, which features images of four-eared bulls, children dressed as matadors and brightly painted ceramics, has been in the family's possession for decades and has never before been seen in Britain. It will be sold at Christie's on 25 June in London, and is estimated to be worth £500,000.

The artworks were given to the family after Picasso – who had long been a lover of bullfighting – formed a close friendship with Dominguin in 1958.

The Dominguin family and Picasso began holidaying regularly in Picasso's southern French villa, in Cannes, with the children growing close to the Spanish artist who often worked in his studio by day and spent time with the family in the evenings.

The intimate works only emerged in the public domain in 2001 as part of a travelling exhibition in Spain, Italy and Switzerland. Teresa Krasny, associate director at Christie's, said that the drawings were often inspired by the various personality quirks of the family.

Many of the images served to show that Picasso had, at times, a "child's way of seeing the world", according to Ms Krasny.

The crayon drawing of the four-eared bull, Taureau aux quatre oreilles, which is estimated to sell for up to £30,000, was created after the couple's eldest son, Miguel, ran into his studio and asked whether Picasso could draw him a picture to celebrate his father's victory in the bull-ring.

Proceeds from the sale will benefit the Museo de los Angeles in Segovia, Spain.