I am afraid I am finding your original query a bit confusing. I think you have got two different Kenneth Munros muddled up.
From the indexes at
www.scotlandspeople.gov.uk:
There is a marriage of Kenneth
Munro to Catherine Forbes on 8 December 1851 in Lochbroom
There is a birth of a Catherine
Munro, mother's surname Forbes, in Lochbroom in 1857, and a death of Catherine Munro, mother's surname Forbes, in Lochbroom in 1
858, aged under 1 year. Not in 1
958.
There is no record of the death of a Catherine Forbes in Ross and Cromarty in either 1857 or 1858.
Catherine Munro, other surname Forbes, mother's maiden surname Mackenzie, died in Lochbroom in 1885, aged 78.
Kenneth Munro, mother's surname Mackenzie, died in Lochbroom in 1893, aged 78.
You say that you have two couples of the same names, both of whom had a daughter Catherine born in Lochbroom on 3 September 1857. Frankly, I think that is extremely unlikely.
There are two marriages of Alexander MacLeods to Catherine Munros, one in 1887 in Kiltearn and one in 1923 in Dingwall. I suggest that you go to
www.scotlandspeople.gov.uk, invest in a few credits and see what the 1887 one tells you.
There are numerous deaths of Catherine M(a)cLeods with other surname M*nr*. There is only one in 1946, in Haymarket in Edinburgh.
There is a death of an Alexander Macleod, aged 85, in Fodderty in 1939.
In the 1891 census, somewhere in Lochbroom, are Kenneth McLeod, 70; son Alexander McLeod, 36, daughter Catherine Mcleod, 34, and son Angus, aged 1. Angus Macleod, mother's maiden surname Munro, was born in Lochbroom in 1889.
In 1901 they are in Resolis; Alexander MacLeod, 50; wife Katty, 43; Angus, 11; Kenneth, 9; Katty, 8y; Jessie, 6; Kenneth J, 2; and
Ann Munro, mother-in-law, widow, 78.
I think you will find that Alexander MacLeod's wife was the daughter of Kenneth Munro and
Ann Mackenzie, and that she was born in Lochbroom in 1856.