The 1855 birth of the un-nammed female (Isabella) might be the most useful record to obtain.
BIRTH
Margaret McKenzie born abt 1852 (didn’t find baptism)
DEATH
Margaret McKenzie died 14 Sept 1856 (age 4), South Leith, Midlothian
Parents - Alexander McKenzie, Margaret Young McKenzie
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BIRTH
Un-nammed female born 20 Feb 1855, Leith, Midlothian
Parents – Margaret Young and Alexander McKenzie
DEATH
Isabella McKenzie died 12 Jun 1856 (age 1) North Leith, Midlothian
Mother - Margaret Young McKenzie. Husband Alex McKenzie
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BIRTH
Alexander McKenzie born 17 September 1856 South Leith, Midlothian
Parents - Alexander McKenzie, Margaret Young McKenzie
DEATH
Alexander McKenzie died 20 Aug 1862 South Leith, Midlothian
Parents - Alexander McKenzie, Margaret Young McKenzie
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BIRTH
John McKenzie born 12 Jun 1858 South Leith, Midlothian
Parents - Alexander McKenzie, Margaret Young McKenzie