Mason Hill, seven, and Ellie Turner, 10, from Haydock, were shocked when Mason's little brother Oaklan had to spend "most of his babyhood" in the Special Care Baby Unit.
Oaklan was born at 34 weeks and then contracted sepsis and jaundice.
The unveiling
After he came home, Legh Vale Primary pupils Mason and Ellie decided to do something to thank the Special Care Baby Unit at Whiston Hospital that saved his life.
They came up with the idea of doing an elastic ball challenge, getting people to guess how many bands had made up the ball.
Those guessing correctly winning prizes ranging from family passes to Knowsley Safari Park to shop vouchers.
On Wednesday, November 27, after months of fundraising and keeping people guessing, Ann Marr, chief executive of the hospital unveiled that they raised £1,285.75 for the hospital...and that the huge elastic band ball was made up of 9,923 elastic bands!
Mason and Ellie with Ann Marr
Speaking after the unveiling on the Special Care Baby Unit, Ellie, said: "I feel proud because I really think it will help the young babies."
Mason's grandmother Sharon Hogan, 52, who also works at the hospital, added: "We all feel very, very emotional, to see that response from staff. It was amazing.
"I've seen the effort the kids have put in and had the motivation to doing it.
"It means a lot here for the family, last time we were here Oaklan was in then before that was Mason was and to know now that these kids walked the streets in the rain to do this, they've done very well.
"I hope their actions will inspire others."
Mason, Ellie and Oaklan
Ann Marr, chief executive of St Helens and Knowsley Hospital Trust, said: "I read about the fundraising before I got invited along. I was amazed two children did this, came up with it and I can't believe the weight of it.
"It's what it's all about that we've provided the medical service and all the other stuff that goes along with having a poorly baby and the support needed for baby, but also parents and siblings as well.
"I know how difficult it can be so it's fantastic to see two children give so much back and I'm also amazed at Ellie's strength holding that elastic ball up for so long and both of them for getting all the community involved. Well done Mason and Ellie."
Lauren Hill, Mason and Oaklan's mum hopes that the money can go towards a sibling room in the ward.
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