The mothers look different, and I'm not sure about the siblings on the suggested match. On the surface they appear to be the same person.
https://www.geni.com/merge/compare/6000000009333023929?to=600000003...
When in England he lived at Newtown House, Newtown, Hampshire and had five children. Darby was married to Mary, daughter of Sir William St Quintin, 4th Baronet and then to Ann Bridges, a widow whose brother was colonial agent and MP, Richard Jackson.[8] Darby's male issue achieved high military rank and held significant wealth:
William Thomas St Quentin (1769-1805) lived at Darby House, Sunbury on Thames and later at Scampston Hall, Malton, Yorkshire
Colonel Matthew Chitty Downes St. Quintin (his son)
Major-General Matthew Chitty Darby-Griffith (1772–1823) lived at Padworth House, Berkshire
https://en.wikipedia.org/wiki/George_Darby