Catastrophe star Rob Delaney has penned an emotional blog informing fans that his 2-year-old son Henry has died following a battle with brain cancer.

The 41-year-old actor shared the "very sad news" on Facebook on Friday, that Henry had been undergoing treatment for a brain tumour on-and-off since early 2017, and sadly passed away in January. 

"My wife and Henry's older brothers and I are devastated of course," he wrote. "Henry was a joy. He was smart, funny, and mischievous and we had so many wonderful adventures together, particularly after he'd moved home following fifteen months living in hospitals.

"His tumor and surgery left him with significant physical disabilities, but he quickly learned sign language and developed his own method of getting from A to B shuffling on his beautiful little bum.

"His drive to live and to love and to connect was profound."

"I am astonished by the love-in-action displayed by Henry's mom and his brothers. They are why I will endeavor to not go mad with grief. I don't want to miss out on their beautiful lives. I'm greedy for more experiences with them. 

"The NHS nurses and doctors and the home carers and charity workers who helped our family survive Henry's illness will be my heroes until the day I die. I am desperately sad right now, but I can say with authority that there is good in this world."

After asking for privacy for his family, Delaney offered a message to Henry. "Thank you, beautiful Henry, for spending as much time with us as you did. We miss you so much," he wrote.

Henry had been diagnosed with a brain tumor shortly after his first birthday, and underwent surgery and other treatment in the first half of 2017, but the cancer returned in autumn.