His Majesty King Bhumibol Adulyadej of Thailand was born on Monday 5 December 1927, being the third and youngest child of Their Royal Highnesses Prince and Princess Mahidol of Songkla.
He is the direct grandson of His Late Majesty King Chulalongkorn or Rama V who was renowned for the great reforms which he made to all institutions of Thailand to bring them up to date and in line with the rest of the Western-orientated world.
Prince Mahidol himself was perhaps one of the most modern-minded of all the sons of King Chulalongkorn and his life was dedicated to the development of many modern ideas particularly in the field of Medical Science so that he is now known as the Father of the Modern Thai Medical Profession.
Last but not least, he was given the significant name of Bhumibol Adulyadej, meaning "Strength of the Land Incomparable Power" which becomes prophetic as his reign advances through various critical periods and the Thai nation evolves more and more around the throne as the sole sources of unity and strength.
Prince Mahidol came back to Thailand and passed away when His Majesty was not yet two years old.
After a brief period of primary schooling in Bangkok, His Majesty left with the rest of his family for Switzerland where he continued his secondary education at the Ecole Nouvelle de la Suisse Romande, Chailly sur Lausanne and received the Bachelieres Letters diploma form the Gymnase Classique Cantonal of Lausanne.
He then chose to enter Lausanne University to study Science, but the death of his elder brother King Ananda Mahidol in Bangkok on 9 June 1946, changed the course of his life completely, for the Law of Succession bestowed on him the arduous but challenging function of the Thai crown.
His Majesty decided to go back to Switzerland for another period of study.
In 1950, His Majesty returned to Thailand for the Coronation Ceremony which took place on 5 May and he went back to Switzerland for another period of study before the urgent call of his country and people brought him back to Thailand in 1951 to stay.
His Majesty met and became engaged on 19 July 1949 to Mom Rajawongse Sirikit, daughter of His Highness Prince Chandaburi Suranath (Mom Chao Nakkhatra Mangala Kitiyakara) and Mom Luang Bua Kitiyakara (nee Mom Luang Bua Snidwongse).
His Highness Prince Chandaburi Suranath was the third son of his Royal Highness Prince Chandaburi Narunath and Her Serene Highness Princess Absarasman Kitiyakara.
Their Majesties were married by Her Majesty Queen Sawang Vadhana, the paternal grandmother of His Majesty, at Sra Pathum Palace in Bangkok on 28 April 1950 and Their Majesties have four children namely:

• Her Royal Highness Princess Ubol Ratana.
• His Royal Highness Crown Prince Maha Vajiralongkorn (was conferred with the title of "Somdech Phra Boroma Orasadhiraj Chao Fah Maha Vajiralongkorn Sayam Makutrajakuman" by His Majesty the King on 28 December 1972) making him the Crown Prince or Heir to the Throne.
• Her Royal Highness Princess Maha Chakri Sirindhorn (was conferred the title of "Somdech Phra Debaratana Rajasuda Chao Fah Maha Chakri Sirindhorn Rathasimakunakornpiyajat Sayam Boroma Rajakumari" by His Majesty the King on 5 December 1977).
• Her Royal Highness Princess Chulabhorn.