Family Mourns Father Who Fought Cancer While Raising Money for Cancer-Stricken Stepdaughter

Both father and daughter were fighting cancer at the same time.

— -- A man who died from terminal cancer after raising hundreds of thousands of dollars to help his cancer-stricken toddler stepdaughter is being remembered in a moving tribute.

The man's wife, Joely Attwater, wrote the moving post titled “I am not ready to let go yet” just a day after her husband, Tom Attwater, died due to an aggressive brain cancer called Glioblastoma.

“Never have I felt so lost and in pain,” she wrote. “Tom was my absolute world and I can’t imagine spending the rest of my life without him. ... I have smiled occasionally, usually at the children, they are an absolute blessing to me right now.”

Tom Attwater was diagnosed with terminal cancer at the same time he and his wife were helping their daughter Kelli with her own cancer battle after she relapsed due to neuroblastoma cancer, a type of cancer that primarily affects children under age 5.

Kelli was initially diagnosed as an infant, but the cancer returned when she was 3 years old -- around the same time her stepfather was diagnosed with terminal cancer, according to the U.K.-based charity Solving Kid’s Cancer.

“It is the worst nightmare possible. We just knew we had to fight for Kelli and stay strong to give her the best chance of life we could,” her parents said of Kelli’s relapse.

Even as he battled cancer, Attwater decided he wanted to continue to help fundraise to ensure Kelli’s medical costs were covered and to help fund research to find a cure for Neuroblastoma, according to the Solve Kid’s Cancer charity, which also noted that Attwater was able to help raise more than 500,000 pounds, or around $750,000 by the beginning of this year.

The day after Attwater’s death, his wife said Kelli was also grieving in her own way.

“Kelli is dealing with her grief in the way a 6 year old deals with most things ... innocently,” Joely Attwater wrote. “She says the sweetest things sometimes and tries her best to help me out in her own special ways.”

The Attwater family declined to comment further to ABC News through the Solve Kid's Cancer charity.