You have not intimated that whether you are govt organisationor not. If you are govt/semi-govt organisation then your action is fully illegal.
In this circumstances it is apparent that :-
(i) your employee intends to deceive his wife and the court by hiding his income.
(ii)In all probability he may have made a false claim.
(iii) His wife wants to contradict his claim and truth to come to the Court.
You cannot in this situatipn expect his wife bhy your simple refusal.
If you wre a govt/semi-govt organisation, then this miscpnduct if proved was sufficient for throwing him out of service.
If you are not a govt/semi-govt organisation you can consutl your own standing order or code of conduct.
In either case the reason advance by your emplpyee (his wife having filed divorce), is not a sufficient to perpetually deny the information nor you have obligatipon or permision to hide iformation for ever.
Now you have two options:-
Option -I
to provide informatipon to her and convince your emplloyee that 2+2=4.
Option-II
compell the lady to get the record summoned to the court (whereever in India the case is ). Then you prepare the record. Send you man to court by paying his TA/DA (or he may take the meagre amlout submitted in Court by applicant).
Your man to travel, regardless of availability of confirmtable and wheather.
Your man to in any case be availble in the court on the summoned date at 10.00 am and keep standing there till called by 5.00 pm.
Your man to repeat the above exerise again, if the mater gets adjourned (due to one rasons or the other) without his evidence.