Kwok and his younger brothers Thomas and Raymond are together referred to by media as the Kwok brothers. Together they controlled the majority of Sun Hung Kai Properties (until ouster in 2008, see below section). As of March 2018, all three brothers were listed in the Forbes 2018 The World's Billionaires, with a net worth of US$16.5 billion (Thomas and Raymond) and US$8 billion (Walter only) respectively. In a separate listing, the Kwok family was listed as the third-richest in Forbes's 2017 Asia's Richest Families, with a net worth of US$40.4 billion as of November 2017. The net worth by Forbes as of his death was US$6.9 billion.
On 18 February 2008, Sun Hung Kai Properties issued a statement saying Kwok would take a temporary leave of absence for personal reasons with immediate effect. Kwok later issued a statement stating he would take a personal holiday to travel to the United States, Beijing and other cities in the coming two to three months, adding he would resume his duties on his return. However, Kwok was formally removed as the chairman on 27 May, with his mother Kwong Siu-hing taking over as chairperson. Kwok remained as one of the non-executive directors until his resignation in 2014.