Wilcombe was born in TA 2984 (SR 1384), the same year as his sister Rosie. He was the third child and second son of Tolman Cotton Sr. and Lily (née Brown) Cotton. Whether they are twins or simply siblings born in the same year is unknown. He has two older siblings, Tolman Cotton Jr. and Rosie Gamgee, wife of Samwise Gamgee. As well as two younger brothers, Bowman (Nick) and Carl (Nibs).