Just revisiting this .... Adalina Black or Hudson died in New Zealand in 1915 and is buried in Sydenham Cemetery in Christchurch. There is a stone inscribed, "In loving memory of Adalina Mary, wife of the late George Hudson of Sunderland, England and only daughter of the late Rev John Black (first General Secretary of the Presbyterian Church of England) died 26th September 1915 aged 61." I also found a newspaper announcement that her funeral would leave the home of her son Robert, 30 Hastings Street, Sydenham.
John Hutchinson's wife was Mary Frances, and she was aged 39 in the 1891 census, so born 1859/60. Therefore she cannot have been a daughter of Adalina Black's husband, who was only 30 in 1881. But the George Hudson who died in 1898 in Middlesbrough was aged 60, so he would have been born 1837/8. Just old enough to have a daughter in 1859, but definitely not old enough to have a son in 1850/1, so Mary Frances cannot be a sister-in-law of Adalina Black or Hudson. Unless her age is wrong in the 1891 census. But it lookas if it's correct - ish.
Aha! .... in 1891 John Hutchinson, 42, and his Mary F, 48, are in the household of his sister-in-law, Elizabeth Walter, single, aged 58. There is a marriage of Mary Frances Walter to John Hutchinson in 1886. Also, there is no record of George and Adalina having any more children. So the J Hutchinson, the son-in-law in whose house George Hudson died in 1898 can't be the one Adelaide Hudson was visiting in 1891 .... can he?
All very confusing.