[Kurtl12]

Jenglow, I've sent you a PM as well. Here is the total crewlist of Wellington X LP198:
Capt. MARQUARD, G. B. 205617V Pilot 70. Sqdn. SAAF 8. A. 12. (C)
Capt. POVEY, R. H. 104048V Navigator 70. Sqdn. SAAF 8. A. 12. (C)
Sgt. MAYLEY, Derek Graham 1800825 Air Bomber 22J. 70. Sqdn. RAFVR 8. A. 12. (C)
F/Sgt. JONES, Rowland Eames 657707 W. Operator 25J. 70. Sqdn. RAF 8. A. 11.
Sgt. ROWE, Alfred 544205 W. Operator 70. Sqdn. RAF 8. A. 12. (C)
The code at the ending reports the grave at the Klagenfurt war cemetery. "(C)" stands for collective grave. Maybe a clue that your cousin was the only crewmember clearly identified?
All the best for your research! Sincerely - Kurtl