This may be a bit of a challenge...
Anyone able to find out where Sir Dyson Marshall KCB was actually born. BTW I believe the date of birth which is out there (1774) to be completely wrong because he joined the East India Military in 1771 (see The East India Military Calendar: Containing the Services of ..., Volume 1).
On the off chance, based on spectulation, he may link with Maj Gen. Josiah Marshall (1772-1845) and with the Marshalls in Ireland, possibly around Fahan and County Donegal. I am assuming he would be born circa 1750-58. He dies in Cawnpore in 1823.
Thanks in advance
James