Advice please

[vtwo]

I am not sure if this is the right place to post if not pls excuse me.
my in laws had applied for their visit visa to come to UK from India and granted for 6 months but due to some un avoidable family problem one of them couldnt travel or use the visa other one came for 2 months and gone back. but they both are planning to come back in April/May for a visit for 6 months.

My question is if they ddnt use the granted visa will there be any problem for them to get another visa?
Is there any time limit to apply for the next visa? the present visa will be expiring in March . will they be able to come in April with new visa?
Do we need to inform the Embassy or consulate for not using the present visa?

Thank you for your time . looking forward to hear from you.
Regards

[vinny]

Shouldn't be a problem if a visa was unused.

See also VAT1.5 Frequency and duration of visits.