According to the memoirs of a Hudson pilot early war crews were generally 2 pilots sharing the navigation, rather than pilot and navigator. Using the Coastal Command Losses Volume I by Ross McNeill most 1939 to 1941 RAF Hudson losses on operations had 4 man crews with the occasional 5 man.
According to the RAAF Organisation Memorandums as of 20 January 1941, Hudson Crew for a General Reconnaissance sortie,
1st Pilot, Officer
2nd Pilot, Officer or Airman
2 x Wireless Air Gunner, Airman
On 22 March the second pilot was upgraded to officer. On 5 March 1942 the same crew for bombing operations as well. As of 8 June 1942 it was changed to
Pilot, Officer
Nav (B), Officer
2 x Wireless Air Gunner, Officer or Airman
Air Gunner, Airman