When 10-year-old Jenna Rohrbach takes the field tonight to sing the National Anthem at the Atlanta Braves' game against the San Francisco Giants, she'll be singing for her sister.

That's because her sister, Alexa, died from cancer three years ago at the age of 11. Tonight is Rally Night at Turner Field in honor of the Atlanta-based Rally Foundation, which raises money to research cures for childhood cancer. Six Rally Kids, who either have fought or are currently fighting cancer, were invited to the pre-game batting practice and the game as guests of the team.

"I’m honored to sing there," said Jenna, a rising sixth-grader at Lost Mountain Middle School. "I know that’s a once in a lifetime chance to be able to sing at the Braves game."

Since her sister's death, Jenna has become very involved with the Rally Foundation, her mother, Robin Rohrbach, said. In fact, Jenna donated the first dollar she received for her allowance to the foundation.

"She’s watched her sister struggle and go through all kinds of different things," Rohrbach said. "This is just part of her life. Her sister was diagnosed before she was born, so Jenna’s kind of lived life as a sibling. From an early age, she’s heard us talk and she told her second grade class what cancer was and that Rally was (raising) money for experiments to try to help kids (suffering) with cancer."

Alexa endured numerous struggles, including going through chemotherapy and radiation when she was 1, being treated at Scottish Rite Children's Hospital and at a hospital in St. Louis, and later going through spinal surgery and having rods put in her back.

"The chemo messed up her lungs, and the radiation messed up her spine," Rohrbach said. "She was only 1, so she was still growing. She had all these side effects that really affected her life later on."

And, one way that Jenna tries to spread awareness for childhood cancer is through singing. She's sung at several high schools, for a Gwinnett Braves game and at Turner Field two years ago.

"She always says, 'I dedicate this to my sister’s memory, Alexa, who died of childhood cancer,'" Rohrbach said.

That's something that Rohrbach said makes her very proud.

"It makes me proud that she’s able to kind of live for her sister, which is what she’s said before," Rohrbach said. She’s said to me, 'I’m going to really live life. I’m going to live for my sister.' As a mom, it just makes me very proud. She’s really doing something special, not just for Alexa but for all the kids who are diagnosed with cancer."

Childhood cancer is treated differently and researched differently, and each year it is underfunded by about $30 million, Rohrbach said. At the Rally Foundation, 93 cents of every dollar goes toward cancer research.

"Our CEO has a really tight budget and makes sure that 93 percent goes into research across the country," Rohrbach said. "For most non-profits, that’s really unheard of. We have a lot of volunteers, a lot of people who have been through this, and they want to be involved and help. So, we really have a barebones administration."

Having the support of Braves catcher Brian McCann, who is a Rally spokesperson, has been instrumental in getting the word out about the grassroots organization, which was started 5-6 years ago, Rohrbach said.

"He and his wife, Ashley, have been very supportive," Rohrbach said. "They’ve talked about Rally at different times. They’ve done a very good job helping support us and get the word out there that there’s an organization out there."

In a news release, McCann said he and his wife are thrilled to host the Rally Kids.

"We feel there couldn’t be a more worthy cause to support," McCann said. "These children go through so much at a young age but show so much courage and strength. It’s amazing and inspiring. No child should ever have to go through it, but if they do, they shouldn’t be alone. Every time we meet a Rally Kid or hear one of their stories, we resolve to do everything we can to help Rally win in their fight against childhood cancer.”