1 year old travelling to UK with grandparents

[tanvkshah]

I am on Tier 2 general visa and my husband is on Tier 2 dependent visa. We both are currently working in UK.
My father in law is suffering from cancer and wanted to spend some time with my son,so I had to keep my son in India for few months when he was around 8 months old.

I am planning to get him back to UK in July'18 with my parents. My plan is for my parents to stay with us for 2-3 months with us in UK so that my son can easily transition from Indian environment to UK environment.

I have got below queries:
a) Is there any issues that comes up with the infant is travelling with grandparents and not parents.
b) Do I need to fill any forms to bring him back, he has already got BRP card (Tier 2 dependent visa) till Feb 2019.