As a general guideline, it is preferable that relatives do not work in the same organization as this could give rise to nepotism. More importantly, if the husband and wife work in the same organization, there could be instances wherein one could face the wrath of superiors at some point, and the other could be praised by the superior. This could lead to embarrassment and ego clashes between them.
Likewise, if both are working in the same organization, they may prefer to take leave on the same date for specific reasons. If one does not get leave while the other is granted leave, the purpose of one availing leave gets defeated.
There could be several underlying issues during the course of their service. Hence, it is recommended that relatives are not engaged in the same company.
Regards