Thomas Killip, the son of James and Sarah, is in the 1871 census aged 8. but not in the 1871 (Sarah is a widow) or 1881 census.
There is a death record for a James Killip in the March quarter of 1865 in Liverpool Vol 8b page 292.
There is also a death record in Liverpool for a 59 year-old Sarah Killip in the March quarter of 1876 Vol. 8b page 127.