UK visitor visa for in-laws

I have a tricky one to apply for. Want to call MIL and FIL over from Pakistan to UK on visitor visa.

Intention is for them to stay 3 months and spend time with both daughters and grandchildren.

However they dont have bank account, they are both old and rely on their sons living with them for living expense. The house is on FIL name so can get a couple of bills which state that on it.

I'd be paying and sponsoring everything.

Any other ideas to make my case stronger please? I will put all these details in the invitation letter