Looking at the 1975 Act and the class of persons able to make a claim under the same, I cannot see whether there is a right for a descendant of a child of the family ie a grandchild or grandchildren to make a claim if their parent has predeceased. Can the grandchild make a claim?
Not unless they were being ‘wholly or partly’ maintained by the deceased immediately before their death. If granny was contributing to school fees, or similar, there might be a claim.
To add to what Iain says, if the deceased treated the grandchild as their own child they could potentially claim, but I would have thought that the grandchild would at least have had to have lived with the deceased to claim in this capacity.