Ancestry have Thomas and Jane on the 1871 and 1881 censuses:
1871 Address - 7, Lylesland, Abbey Burgh, Renfrewshire.
Thomas Allan 49, born Montalk, Perthshire, starch maker
Jane Allan 47, Denny, Stirlingshire
John 21 Campsie, Thomas (no age) Campsie, James 27 Paisley, Janet 14 Paisley, William 12 Neilston, Alex 9 Paisley, David 6 Paisley, Jane 3 Paisley
1881 Address - not given
Thomas Allan 59, born Kincardine Perthshire, starchwork worker
Jane 55 Denny, Alexander 18, David 16, Jane 13
Thomas, Jane and family are on the 1891 Canadian Census so emigrated sometime between the two censuses. Not seeing William on any 1881 census so far.
Scotlands People have Thomas's baptism:
Allan Thomas - Peter Allan & Kath. McBeath - 22.10.1821 - parish Kincardine.
Only one other child appears on SP and Family Search for those parents: the James born Tibbermore 7.12.1823