Known as Theo, his support of his older brother's artistic ambitions and well-being allowed Vincent to devote himself entirely to painting.

Theodorus "Theo" van Gogh[1] was born on 1 May 1857 in the village of Groot-Zundert in the province of North Brabant, Netherlands.

[5] By 1884, he was transferred to the Paris main office, which in 1884 took the name of Boussod, Valadon & Cie.[6] Beginning in the winter of 1880–1881, he sent painting materials as well as monthly financial support[7] to his brother Vincent, who was living in Belgium and soon moved to the Netherlands.

During their short engagement, they had an extensive correspondence, later published as Brief Happiness,[8] in which they discussed practical matters of setting up married life together, but Theo also conveyed strength and the importance of his bond with Vincent.

Theo suffered from dementia paralytica, now understood as late-stage neurosyphilis,[9][10][11][12] and his health declined rapidly after Vincent's death.

Weak and unable to come to terms with Vincent's absence, he died six months later (25 January 1891) at age 33 in Den Dolder.

Theo was equally the one with whom Gauguin communicated when his relationship with Vincent turned volatile and unmanageable, notably the severing of the ear fiasco.

Theo was the source of stability and the intermediate between the two artists and allowed them to create prolifically for a couple of months (63 days); paintings that would otherwise not have survived.

[6] Theo also had close relations with Camille Pissarro, and in the autumn of 1888, he presented a few of the painter's latest works, eventually devoting an exhibit to him in 1890.

Theo was also interested in Alfred Sisley, Pierre-Auguste Renoir, and other "moderns" such as Paul-Albert Besnard, Eugène Carrière, and Jean-François Raffaëlli.

[24] These letters witness both the emotional and professional state of Vincent throughout his life as early as 1874 and serve as a diary for his everyday encounters.

[26][27] The Van Gogh brothers' relationship figured in the Vincente Minnelli 1956 movie adaptation of Irving Stone's 1934 biographical novel Lust for Life.

In it, Hollywood star Kirk Douglas played Vincent, and British actor James Donald appeared as Theo.

The brothers' relationship is also featured in Maurice Pialat's 1991 film Van Gogh, with Jacques Dutronc playing Vincent and Bernard Le Coq as Theo.

By 1 December his medical notes confirmed he presented all the symptoms of dementia paralytica, a disease of the brain caused by syphilis.