In the legislation for Inheritance (Provision for Dependants) Act 1975 it states that "any person (not being a person included in the foregoing paragraphs of this subsection) who immediately before the death of the deceased was being maintained, either wholly or partly, by the deceased" can claim under the Act.
If a couple are both earning a similar amount of money and have no dependent children could it reasonably be argued that one maintains the other if they share household bills? It is being alleged that a family member maintained his partner by paying half of the rent and utilities, but I do not believe this is really maintenance.
Just because one member of the couple has the monthly payments set up to come from their account and the other person reimburses them for their fair share, surely this is not maintaining them? To draw a parallel, if a group of 5 people go out for dinner and one pays the full bill on their credit card with the others reimbursing that person 1/5 each, are any of them maintaining the payee? Surely not.