They are raising funds and remembering a loved one on the night
27 year old Thomas O'Donoghue was due to take part in the event with his older brother Peter but he died in March after a brief battle with cancer.
Ahead of tonight's event a fundraiser set up in his name has so far raised €13,000 for Focus Ireland.
Thomas regularly raised funds for Cork's homeless and Peter felt that it was a fitting tribute to his kind hearted brother to take part in the Big Rebel Sleep Out and raise as much money as he can in Thomas' name.
Speaking to RedFM News Peter says he along with his family members from around the world will take part in tonight's Big Rebel Sleep Out:
