Dear Sanjay,
On humanitarian grounds, you may accede to their request but then there is another side too. What if you start getting similar requests from other staff members? Now someone has approached you for relaxation in working hours because of a child, next time it could be a parent's sickness.
It could become a trend and managing the company activities could pose a challenge. If you say 'yes' to them then saying 'no' to others would be difficult and if you say 'no' now, saying 'no' would be easy in future.
However, you may check for how long the couple has been working in the company, whether they were employees even before their marriage and workplace was the cause of their marriage etc.
Thanks,
Dinesh Divekar