Huxley came from the Huxley family on his father's side and the Arnold family on his mother's.
His great-grandfather was Thomas Arnold of Rugby School, his great-uncle Matthew Arnold, and his aunt Mrs Humphrey Ward.
His grandfather was Thomas Henry Huxley, a friend and supporter of Charles Darwin and proponent of evolution, and his father was writer and editor Leonard Huxley.

Huxley's mother was Julia Arnold (1862-1908), a graduate of Somerville College,  Oxford, who had gained a First in English Literature there in 1882.
Julia and Leonard married in 1885 and they had four children: Margaret (1899-1981), the novelist Aldous, Trevenen and Julian.

Huxley was born on 22 June 1887, at the London house of his aunt.
His mother died in 1908, when he was 21.
In 1912, his father married Rosalind Bruce, who was the same age as Julian, and he later acquired step-brothers Andrew Huxley and David Huxley.

In 1911, Huxley became informally engaged to  Kathleen Fordham, whom he had met some years earlier when she was a pupil at Prior's Field, the school his mother had run.
During 1913 the relationship broke down  and Huxley had a nervous breakdown which a biographer described as caused by 'conflict between desire and guilt'.
In the first months of 1914 Huxley had severe depression and lived for some weeks at The Hermitage, a small private nursing home.
In August of 1914 while Huxley was in Scotland, his brother Trevenen also had a nervous breakdown and stayed in the same nursing home.
Trevenen was worried about how he had treated one of his women friends and committed suicide whilst there.

In 1919 Huxley married Juliette Baillot (1896–1994) a French Swiss woman whom he had met while she was employed as a governess at Garsington Manor, the country house of Lady Ottoline Morrell.
Huxley was later unfaithful to Baillot and told her that he wanted an open marriage.
One of his affairs was with the poet May Sarton who in turn fell in love with Baillot and had a brief affair with her as well.
Huxley described himself in print as suffering from manic depression, and his wife's autobiography suggests that Julian Huxley suffered from  a bipolar disorder.
He relied on his wife to provide moral and practical support throughout his life.

Julian and Juliette Huxley had two sons, Anthony Huxley (1920–1992) and Francis Huxley (1923–2016), who both became scientists.
Huxley came from the Huxley family on his father's side and the Arnold family on his mother's. His great-grandfather was Thomas Arnold of Rugby School, his great-uncle Matthew Arnold, and his aunt Mrs Humphrey Ward. His grandfather was Thomas Henry Huxley, a friend and supporter of Charles Darwin and proponent of evolution, and his father was writer and editor Leonard Huxley. 
Huxley's mother was Julia Arnold (1862-1908), a graduate of Somerville College,  Oxford, who had gained a First in English Literature there in 1882. Julia and Leonard married in 1885 and they had four children: Margaret (1899-1981), the novelist Aldous, Trevenen and Julian.
Huxley was born on 22 June 1887, at the London house of his aunt. His mother died in 1908, when he was 21. In 1912, his father married Rosalind Bruce, who was the same age as Julian, and he later acquired step-brothers Andrew Huxley and David Huxley. 
In 1911, Huxley became informally engaged to  Kathleen Fordham, whom he had met some years earlier when she was a pupil at Prior's Field, the school his mother had run. During 1913 the relationship broke down  and Huxley had a nervous breakdown which a biographer described as caused by 'conflict between desire and guilt'. In the first months of 1914 Huxley had severe depression and lived for some weeks at The Hermitage, a small private nursing home. In August of 1914 while Huxley was in Scotland, his brother Trevenen also had a nervous breakdown and stayed in the same nursing home. Trevenen was worried about how he had treated one of his women friends and committed suicide whilst there.
In 1919 Huxley married Juliette Baillot (1896–1994) a French Swiss woman whom he had met while she was employed as a governess at Garsington Manor, the country house of Lady Ottoline Morrell. Huxley was later unfaithful to Baillot and told her that he wanted an open marriage. One of his affairs was with the poet May Sarton who in turn fell in love with Baillot and had a brief affair with her as well. Huxley described himself in print as suffering from manic depression, and his wife's autobiography suggests that Julian Huxley suffered from  a bipolar disorder. He relied on his wife to provide moral and practical support throughout his life. 
Julian and Juliette Huxley had two sons, Anthony Huxley (1920–1992) and Francis Huxley (1923–2016), who both became scientists.
Julian Huxley