Farmer was born a
fraternal twin in
Westerham, Kent, on 14 June 1939, as the third child of Hugh Robert MacDonald (died 26 May 2004) and Penelope Boothby Farmer. Her parents and hospital staff were unaware of her existence until some 25 minutes after the birth of her twin sister Judith. Throughout Farmer's life, twinship has been a defining element in her understanding of her identity. The importance of Farmer's relationship with her twin sister Judith was reflected in her books, having published
Two, or: The Book of Twins and Doubles in 1996, and
Sisters: An Anthology in 1999. The twins have an older brother, Tim, and a younger sister, Sally. After attending a
boarding school, she read history at
St Anne's College, Oxford and did postgraduate work at
Bedford College, University of London. She visited South Africa in 1994, talking with people about their views on the election. She later wrote an article about this, published in the
Index on Censorship. In 2000, Farmer published an article about the challenges facing the Hong Kong Chinese community in the UK. According to Penelope Farmer's personal blog site, she was in 2012 living on
Lanzarote in the
Canary Islands. She there described herself as "a writer – published for many years, now struggling", and listed "her grandchildren" among those she loved and missed. Other relations were mentioned: the departure of her daughter and a granddaughter (23 April 2004). The 22 April 2010 entry states that her son was among those staying with her, with his daughters aged eight and twelve. ==Writing career==