Hi Peter,
You are the first person I have met who is descended from John Roy and Ann Marshall. Yes I know that John re-married his first cousin. Their son John (my great grandfather) married Jessie McKillip (or Janet Cumming Keil) and their daughter Christina married my grandfather Alexander Sandilands Rennie. Janet Cumming Keil was illegitimate and later took the name of her father, McKillip. Below is a timeline of events and descendants of John and Janet.
Marriage
John Roy married Janet Cumming Keil on June 30, 1882, when he was 19 years old and Janet Cumming Keil (1861–1936) age 22, at the District of St Mary, Burgh of Dundee.
ABT 1882
* Birth of Son
His son John was born in 1882 in St Martins, Perthshire.
10 AUG 1884
Birth of Daughter
His daughter Christina was born on August 10, 1884, in St Martins, Perthshire.
ABT 1888
Birth of Son
His son James was born in 1888 in Cargill, Perthshire.
ABT 1889
** Birth of Son
His son Frank Buttar was born in 1889 in Kilspindie, Perthshire.
ABT 1892
Birth of Son
His son Charles was born in 1892 in Kinnoull, Perthshire.
ABT 1893
Birth of Daughter
His daughter Jessie Ann was born in 1893 in Kinnaird, Perthshire.
ABT 1897
Birth of Daughter
His daughter Isabella was born in 1897 in Cargill, Perthshire.
ABT 1899
Birth of Daughter
His daughter Betsy was born in 1899 in Cargill, Perthshire.
ABT 1901
Birth of Daughter
His daughter Fanny Brown was born in 1901 in Cargill, Perthshire.
29 OCT 1936
Death of Wife
His wife Janet Cumming passed away on October 29, 1936, at the age of 75, Ruthven Avenue, Perth. They had been married 54 years.
* Birth certificate shows he was born illegitimate to John Roy and Jessie McKillop.
** Birth certificate shows he was born illegitimate to John Roy and Margaret Emslie m.s. Buttar (widow). Frank is with the family of John Roy and Jessie McKillop on the 1891 and the 1901 census and recorded as son. Frank's death certificate confirms his birth parents as shown on the birth certificate. I found the death certificate, 1938, of a Margaret Drummond m.s. Buttar, widow of (1) John Emslie and (2) George Drummond. From the index of marriages on ScotlandsPeople, Margaret and George married in 1897.
Apart from my direct line from daughter Christina, I have no information on her siblings' descendants. The furthest back I have gone on the direct line of our Roy ancestry is to a John Roy and his wife Janet Christie; their son Duncan (1785-1871) and his wife Betty Watson. Possibly you know that already. I sometimes wonder if our Roy family is connected to the celebrated Rob Roy McGregor, any thoughts?
If you want details of John Roy and Ann Marshall's other children, I can pass on to you.
You will find Dr Marshall's will on the Scotland's People site and that of his brother, John, who died at the age of 43 in Brazil.
I am no longer a member of ancestry.com and only ever had a free trial subscription but luckily I can still access to view and update my tree.
I find that I only now open my ancestry when someone is asking for information re my ancestors. So new inquiries are always welcome lest I forget my past.
Anway happy hunting.
Liz
ps I was brought up in Perth and never knew anything about nor was interested in these ancestors at the time.