The late star's daughter shared a story at Comic Relief Live about how her father gave back by hiring homeless people for every tour or film he did

"It was deeply important to him to help improve the human condition," Zak tells PEOPLE of his dad, who died in 2014 at age 63

"I was lucky enough to have some great interactions with Robin Williams before he passed," O’Brien shared of the late actor, who died in August 2014