Some bonds are so strong, not even death can break them. For Bailey Cooper, a nine-year-old boy from the UK, that bond was with his baby sister, Millie—a little girl he fought desperately to meet before saying goodbye.

Bailey’s battle with Non-Hodgkin’s lymphoma was long and painful. After multiple rounds of treatment, his cancer kept returning. But when his mother, Rachel, became pregnant, Bailey clung to one goal: meeting his sister.

Millie arrived in November, and Bailey named her, choosing a word that meant “gentle strength.” For the next month, he cuddled her, kissed her, and whispered to her, as if trying to give her a lifetime of love in just a few short weeks.

As his body failed him, Bailey made plans for his family’s future. He picked out Christmas gifts for his little brother, knowing he wouldn’t be there to enjoy them. He asked his parents to wear superhero costumes to his funeral—because, in his eyes, they were the real heroes.

On Christmas Eve, with Millie in his arms, Bailey took his final breath. His family told him it was okay to let go, and with one last tear, he did.

Hundreds came to say goodbye, including his football idol, Tom Lockyer. Bailey’s story is one of courage, love, and the unshakable bond between siblings. Though his time was short, his light will never dim.