Thank you to all of you!!
I did go look at more of Fulham's Ushers, and there are a few more without a mmn listed on the GRO index, which makes me believe they are Illegitimate + I couldn't find a census for them.
Edit: putting them here for now, i'll do more research on them soon.
USHER, WILLIAM JOSEPH -
GRO Reference: 1898 S Quarter in FULHAM Volume 01A Page 212
USHER, IVY ELIZABETH -
GRO Reference: 1902 J Quarter in FULHAM Volume 01A Page 217
USHER, GERTRUDE BESSIE DRAKE -
GRO Reference: 1904 S Quarter in FULHAM Volume 01A Page 210
USHER, IVY -
GRO Reference: 1906 M Quarter in FULHAM Volume 01A Page 355
^ does seem to have an 1911 census, living with completely unrelated people.