Former King of Spain recalls killing younger brother by shooting him in forehead as a teenager

Spain's exiled king has revealed for the first time exactly how he shot and killed his younger brother in a tragic incident nearly 70 years ago.

Juan Carlos I became Spain's ruler in 1975 and ruled for 39 years until his abdication in 2014, which came in the wake of several scandals and a decline in popularity.

It was alleged that the member of the Spanish Royal Family bedded over 2,000 women during his time as king, despite remaining married to his wife, Sofia of Spain, for the entirety of his reign.

But it was a lavish holiday that proved to be the final straw, which saw him hand over the reign to his son Felipe VI. It came at a time when Spain was in recession and 50 percent of young people were unemployed.

Juan Carlos, now 87, moved to Dubai with his wife, and he's now released a memoir in which he reflects on his reign and life, with one chapter focusing on the incident which saw his younger brother Infante Alfonso killed when he was just 14.

Juan Carlos's memoir will be released next month (Elena Fernandez/Europa Press via Getty Images)

In the two-page chapter, he reveals that he and his younger brother were 'playing' with a pistol in their family's home in Portugal in 1956.

He writes: "I will not recover from this tragedy. Its gravity will accompany me forever. We had taken out the magazine. We had no idea there was a bullet left in the chamber.

"A shot was fired into the air, the bullet ricocheted and struck my brother squarely in the forehead. He died in our father’s arms."

Juan Carlos was 18, but there was no inquiry into his younger brother's death, with Juan's father throwing the pistol into the sea and covering Alfonso's body with the Spanish flag.

A rare picture of the two brothers together (Reddit)

The disgraced former king suggests that his father shook him, demanding that he promise it wasn't done on purpose. But their relationship was never the same, as he returned to the military academy.

He added: "There is a before and an after. It is still difficult for me to speak of it, and I think of it every day … I miss him; I wish I could have him by my side and talk with him.

"I lost a friend, a confidant. He left me with an immense emptiness. Without his death, my life would have been less dark, less unhappy."

The book will be released in Spanish next month, to coincide with the 50th anniversary of the dictator Franco's death, and the restoration of the monarchy in Spain.