Merge is impossible

What causes this issue?

Both central persons of the personnel numbers &V1& and &V2& have
relationships and/or infotypes.

System Response

The personnel numbers &V1& and &V2& have not been merged.

How to fix this error?

Please check both central persons and delete all relationships (except
for 'B209') and infotypes from one central person. Then the personnel
numbers &V1& and &V2& can be merged under the other central person.

Procedure for System Administrators

The system issues an error message and will not allow you to continue with this transaction until the error is resolved.

Error message extract from SAP system. Copyright SAP SE.