The comedian has revealed his beloved mum Barbara is battling the disease after surviving a number of bouts during his childhood, including uterus cancer when Russell was eight and breast cancer a year later.
Katy Perry filmed her sister's birth on her mobile phone.
The 'Roar' hitmaker was by her older sibling Angela Hudson's side last week when she welcomed her little girl into the world, and although she helped deliver her niece 29-year-old pop star still managed to capture the moment on film.
Katy Perry broke up with John Mayer because he kept breaking promises.
The 'Teenage Dream' singer had an on/off relationship with the guitar player from 2012, but they decided to finally split last month, blaming her upcoming Prismatic tour, although a source claims there was more to it than conflicting schedules.