sanjay gupta introduces us to bruce feiler, a devoted husband, father and writer who overcame a rare bone cancer. >> reporter: i first met bruce three years ago when he was trying to rebound from a cancer diagnosis, grappling with the possibility of dying before his twin daughters, eden and tybee, grew up. facing his own mortality. >> i could just feel my body sort of slipping away. >> reporter: he makes an extraordinary request. >> will you help be their dad? >> reporter: thankfully, bruce and his family got through that. and today bruce has no evidence of cancer in his body. with all that behind him, he has resumed doing what he does best, writing. his new book is called "the secrets of happy families." what inspired you to write this book? >> we were always on the defense. and that's what it's like to be a parent these days. we made a list of all of the things that the kids have to do in the mornings. and then here's the key. they have to check off their own lists. a lot of what we are doing here is trying to kind of bring them into the process, be less top down, be less kind of pa