Hi EDO
I am unsure which link you are referring to . Is it the link between Charles the architect and William the Attorney? I looked William up in "Kings Inns Admission Papers" but the entry is quite sparse saying only that he was an attorney in 1799.
If we assume that Charles and William were brothers, their father was Rev Edward Cottrell 1708-1788, who was the son of Alderman Francis Cottrell d. 1716 who was Mayor of Cork in 1703. These links are documented by various leases and deeds.
You said that Richard was catholic. Charles was protestant but the difference in religion does not surprise me as in my own family,Jermyn, there are a number of mixed marriages at much the same time. Marriages between the same class may have been more important than religion.
John Cottrell is a new one to me but will be added to my list of unattached Cottrells. Any info you would like,just ask
Andy