William Crombie b. 1862 Carnwath, Lanarkshire

[Cass Ainslie]

William Crombie is recorded as a clerk aged 19 on the 1881 Scotland census.
He married Janet Seggie in 1883, in West Calder, Edinburgh. They had 4 daughters by 1890 when he was an accounts clerk in Heaton, (Lancs?)
Janet died in 1897 I think, and by 1899 William had married Mary Cassidy in Newcastle Upon Tyne and had another daughter Williamina.
Mary, her 2 year old daughter and 3 of her step daughters are on a 1901 England census, but William is missing. I can't find any William Crombie on either an English or Scottish 1901 census matching his age or profession.
He does reappear by 1911 ( they have a son, Willie in 1903) and the older girls have left home.
Can anyone help solve the puzzle of where William had gone, or was it normal to omit the head of the house if he were just out working?
Thank you in advance for any help you can give.