I think I've found Emily and Martha on the 1871:
15 Belgrave St, Stepney
RG10/547 f.134 p.10
Martha (looks rather like 'Matha' on the original image, the handwriting is bad) Br??? (could well be 'Brewer'), 55, house proprietor, born Windsor Berks
Emily Hurtell, 26, daughter, married, sailor's wife, b. Wapping
if Alexander was away at sea he may have been missed off the census.