I am gradually coming to the conclusion that for some reason or other Henry and Caroline never married. Henry died in 1902, so I think Caroline (as a widow) would not need to answer the question about years married and numbers of children on the 1911 census. But she did. The number of children born and those died match with what I have found (and surmised) from Portsea / Portsmouth reg district bmds. So I think what she has stated is accurate there. But what does she state for number of years married? !!
From 1881, 1891 and 1901 census records we have 10 known children.
Alfred Henry J Q4 1876 2b 492
William Thomas Q2 1879 2b 518
Elizabeth Harriet Q4 1880 2b 488 died age 0 Q3 1881 2b 267
Frederick Q2 1882 2b 524
James Q3 1885 2b 440
Charles Q2 1887 2b 479 died age 20 Q3 1909 2b 245
Florence Q2 1889 2b 527
Ernest Norman Q4 1890 2b 443 died age 0 Q2 1891 2b 363
Arthur Q2 1892 2b 488
Elsie Gertrude Q3 1898 2b 517
Three had died before 1911.
By eliminating other births in Portsea either by belonging to other Glew families or too close to a known child of Henry and Caroline, I come up with only three more who were born and died between censuses. These seem the strongest possibilities for the "missing" children
Edith Ellen Q1 1878 2b 529 died age 0 Q4 1878 2b 316
Thomas Q2 1884 2b 555 died age 2 Q2 1886 2b 297
Nellie Caroline Q1 1895 2b 514 died age 1 Q3 1896 2b 317
So what do we know about Caroline? Censuses and age at death put her year of birth between 1854 and 1858. She was most likely born in Bristol although 1881 has Littleton Sussex (abbreviation for Littlehampton perhaps?). She would have had her first child at the age of 18 - 22 depending on her actual age. Likely to be under 21 when she got together with Henry, possibly parental consent was refused for them to marry and they never got round to it after she turned 21.
Why would a girl of her age have come from Bristol to Portsmouth? I would have thought Bristol would have had plenty of opportunities for a girl to work, or if not she might move to London. Bristol and Portsmouth are both seaports, perhaps her father was a sailor?
Possibility her maiden name is King - information from her son Arthur's death record in Canada. If the informant had Arthur's birth certificate this should be accurate, but if the informant was just vaguely remembering something he / she was told a long time before - who knows?