In search of answers, publishers approached Auma Obama, the president's paternal half-sister, to write a book. Barack grew up in the US and Indonesia, while his sister Auma, who is one year his senior, was raised in the Kenyan village of Alego Nyangoma, which was the birthplace of their father.

But the book Auma has written about the life of her world-famous brother is not a biography of him.

"I really didn't want to write about Barack. Besides, it's really not my place to tell his story," Auma said during an interview in Johannesburg, where she was promoting her book, And Then Life Happens.

"The story I've always wanted to tell is the story of my family and how we experienced and lived in so many different cultures."

Her book, a candid and reflective memoir, begins with a character sketch of her father, Barack Obama Snr - a smart, studious man who left his first wife, Kieza, on the family compound while she was pregnant with Auma so he could pursue a scholarship at the University of Hawaii. During his time abroad, he met Stanley Ann Dunham, whom he married after she fell pregnant with Barack Obama Jnr.

They later divorced and he went on to graduate with a degree in Economics at Harvard University. He then married his third wife - in his Lou culture, polygamy was acceptable - Ruth Baker, a middle-class white American who followed him to Nairobi. Auma's parents separated and Auma and her older brother, Abongo, lived with their father and his new wife.

After Baker left her father, Auma found the family home became a place with an "oppressive emptiness" and she resented her father for it.

"I blamed him because I guess at that time I didn't see the bigger picture. I didn't know or understand the adult world. All I could see was my pain and what was missing for me."

She found comfort in books, especially German literature, and did well at school. This led to her travelling to Germany as an exchange student.

Despite Auma not revealing too much about her powerful brother, it's an engrossing memoir that enriches the reader's understanding of the complex Obama family dynamics and how they bridge Western and African cultures.

'And Then Life Happens' is published by Pan MacMillan and is available from Exclusive Books for R236