As far as I know, Khushwant Singh was not generous in the sense of famous people who donate large sums of money to charitable causes. But through his own writings and from writing from others about him, there are instances and events that would lead one to believe he was overall, a generous man.
An online obituary, written by Reginald Massey in 2014, states, “Professionally, he was always generous, open to ideas and innovations and, above all, big-hearted. Every evening from seven onwards his numerous friends, Indians and foreigners, would visit him. This was Johnnie Walker and talk time, presided over by a host who was endlessly interesting and witty.”