The BDM database at the DIA is your friend!!
https://www.bdmhistoricalrecords.dia.govt.nz/search
Births, deaths and marriages are kept seperate. Below you can find - your great grandparents birth, marriage and death records, their parents marriages and most of the siblings!! No children yet since 100 years has not yet passed since the wedding.
Birth registrations
1905/9814 McLean Peter Frederick Janet Harold Percy Charles
1909/2412 Molesworth Mary Graham Mary David
Marriage registrations
1927/9122 Mary Graham Molesworth Peter Frederick McLean
Death registrations - including dates of birth
1978/37433 McLean Peter Frederick 2 December 1904
1979/34773 McLean Mary Graham 9 January 1909
Marriages of parents
1904/2977 Janet Collett Harold Percy Charles McLean
1902/3738 Mary Smith David Molesworth
Siblings
1905/9814 McLean Peter Frederick Janet Harold Percy Charles
1906/6933 McLean Harold Bernard Janet Harold Percy Charles
1910/8041 McLean Janet Emmie Janet Harold Percy Charles
1913/609 Molesworth Stanley George Mary David -
1905/2271 Molesworth Theophilus Gordon Mary David -
1904/15358 Molesworth Desmond Mary David
1903/17433 Molesworth Edward Powell Mary David
1906/13274 Molesworth Lorna Frances Mary David
1907/19940 Molesworth Caroline Dorothy Mary David
1909/2412 Molesworth Mary Graham Mary David
1917/9292 Molesworth Olwen Mary David
1910/7716 Molesworth Vera Mary David
I hope these details are helpful!!
This is all the RAW data.
If you need any help to interpret them, just add a comment.
Robynne