Christine Coates, 59, has looked after Erica, 20, Phillip, 16, and Casey, 11, since her youngest daughter Jayne Coates, 34, died of cervical cancer in 2007.
She has also supported eldest daughter Jill Mallinder, 40, after her son Ryan, 11, was diagnosed with a rare form of cancer.
Christine, of Crookes Lane, was nominated by nieces Kerry Parkin and Vicky Wallace.
Kerry, 39, of Manor Farm Close, Carlton, said: "Despite the difficult times she has undergone she is still there to support others in times of need and I want her to know that she is loved and appreciated and deserves a special mention."
Grandson Ryan, 11, discovered he had Ewing's Sarcoma in 2011 and has undergone chemotherapy and radiotherapy over the last 12 months.
Christine, who is the steward of Carlton WMC, helped daughter Jill by staying at the hospital with Ryan or looking after her two other children, Ellis, 2, and seven-month old Ella.
She also does a lot of charity work and recently raised £2,000 for Sheffield Children's Hospital as well as fundraising for Help for Heroes.