Family is overweight what to do.

[Lucas D]

My mom is overweight and she knows it and is trying but is too stubborn(i.e. wont put down icecream). My sister just doesnt know and i dont want to hurt her feelings. She weighs more than me and is three and a half years younger (10). What can i do. any help is appreciated.
Sister has to start eventually and personal trainer is out of the question suttle things please.