Gan married his first wife, Koh Chwee Neo, at the age of 18, and in 1859 adopted his first son, Gan Tiang Tock, who was an important partner in the building of his fortune.
Gan menikahi istri pertamanya, Koh Chwee Neo, pada usia 18 tahun, dan oada 1859 mengadopsi putra pertamanya, Gan Tiang Tock, yang merupakan seorang partner berpengaruh dalam pembangunan kekayaannya.