Hi,
In most of the Companies they dont prefer close relatives working in same dept. Like Brothers, Sisters, Husband and wife reason being either one of them might show some favour for the other provided they are immediate superior to the other.
Other negative point is in case of some family function both of them will expect leave which might affect work.
In case of any free mediclaim offered by the company for the whole family then only one member can be given the benefit as the other will be covered under family option and no need for separate cover.
Otherwise if both of them are key performers with some special skills then companies don't mind hiring even for same dept