I suspect that Glenys has at least two different people here.
A Drum Major in a Native Infantry Regiment (where did you get his name?)
would have been either a native Indian (unlikely if he had a European name)
or an Anglo-Indian. As such, he would not have been able to progress to the
position of 'Overseer' of the 'Department of Public Works' (DPW).
You will have to choose which possible 'ancestor' you wish to pursue. The
first will be extremely difficult. The second rather easy. You may wish to
pursue his career 'backwards' to find in which ship/year he arrived in
India. Then his origin will be relatively easy to determine in the military
records. Any career in the DPW and Police should be found in the V12 records
at the India Office Records
Families in British India Society