Donald McLennan is on geni.com married to
Maria Cleaver
NSW BDM birth registration V1851987 56/1851. Parents: George and Eliza. at Windsor.
No NSW BDM death registration found.
I believe the Maria Cleaver he did marry is:
Maria McLennan
Marriage registration is 3252/1876 at Manning River
Death registration is 10436/1934 parents are John and Charlotte, Taree district.
Reasons
1. Donald McLennan lived in the Manning River district. Whereas Maria Cleaver, Maria Cleaver was born in the Windsor District and the family moved to Mudgee.
2. Maria Cleaver's, Maria McLennan , family (John and Charlotte Cleaver and four sisters and two brothers) were pioneers in the Manning River District.
3. Evidence that the Maria Cleaver of the Manning District may have been born in 1853, not 1851:
https://www.findagrave.com/memorial/50573737/maria-mclennan
Findagrave gives the birthdate of Maria McLennan as 1851 and her age at death on her headstone is "81 years". If the age is correct that would make her born in 1853 not 1851.
There is a reference to Maria Cleaver born in 1853 to John and Charlotte Cleaver of the Manning river district in Mid North Coast Pioneers website. The source is "Pre 1860 Pioneer Register, Book 2", citation details #857. Published by the Manning Wallamba Family History Society in 2004.
see entry for Maria McLennan (Cleaver) here: http://mncp.scss.dyndns.info/individual.php?pid=I43119&ged=Greg...
Obituary for the wife of Donald McLennan states that her siblings were the chldren of John Cleaver, Snr, Free Settler "Woolmer Castle" 1848 and Charlotte Cleaver, Free Settler "Woolmer Castle" 1848 of Manning River.
Maria McLennan see the profile overview
Brothers and sisters of deceased were: Mr. John Cleaver, The Bight, near Wingham; Mr. William Cleaver, Kimbriki; Mrs. George Greenslade (Marion), South Australia; Mrs. William Lean (Charlotte), Bellinger River, whose husband originally came from Dungog; Mrs. D. Lee (Eliza), Port Macquarie; and Mrs. Emma Jane Higglns (South Coast). The remains were laid to rest in the Redbank cemetery, beside those of her late husband