2. What are disadvantage of keeping married couple in same department except leave taken at same time ?
3.Advantage is longer stability and bonding with organisation . If leave could affect , change one of them's department .
Sometimes if department or nature of work is sensitive, probably they can be kept separate.
As a matter of fact, removal of one of the pair, due to fact of marriage can go legally against the company.
Apart from legality, in my view, to look at husband and wife working in the same company/department with apprehension of potential problem is immature and unhealthy.
Yes, if they give reasons due to their conduct or work habits which adversely affects the working of the company or department.
In such a situation of proven nature, at the most action of transferring or changing the role may be called for but certainly not making one of the partners to leave.
Therefore , your organisation should give them full opportunity to work with positive attitude unless and until they prove themselves unworthy of your belief and faith by their conduct.