I'll go back a bit further. Jane Grieve married my great grandfather William Laughlan on 16 October 1855 in St Patricks, Partick, Renfrew.
Children were John, William John, (my grandfather) George Hepburn, Jane Galloway, Catherine Laughlan.

The name William Laughlan went for 3 generations.

Jane Grieves father was Peter Grieve 1805-1855 and mother was Jane Galloway (1803-1878

The 1841 Census shows him (Peter) to be 35 in 1841, thus born in 1805-6.

I only have two children listed for Peter & Jane - Jane Grieve (1835) and John (1825) tho there are apparently some more in between.

The 1851 census shows John now 26 and born in 1825, widower - his son John 3, and his mother Jean Galloway, widow aged 44, thus born in 1807.

I had Peters parents as Alexander Grieve & Catherine Taylor (note Jane Grieve and William Laughlan called one of their daughters Catherine, and other family names were Jane, John & William.

In answer to your question, I really don't know the relationship of Mary though.