Family visit visa - proving relationship

Hi,

On behalf of an applicant I am helping,

The applicant's aunt (mother's sister) is a retired British Citizen living in the UK. The applicant is an Iranian national and wishes to apply for a family visit visa to visit England for 2 weeks later this year.

What documents would you suggest to provide evidence of the relationship? I am sure birth certificates of the aunt, mother and applicant to show the common ancestry would be fine, but they will all need translating from Farsi. Would passport ID pages showing a common surname/fathers' name for the aunt and mother, plus the applicant's birth certificate, be sufficient?

The applicant will be staying in her aunt's spare room in their own property. What documents should be submitted as evidence of this? Would utility bills or council tax statements plus a photograph of the spare room be sufficient?

Finally, the guidance talks about evidence of intention to visit the family member. Other than a letter of invitation from the aunt and an email conversation between the applicant and her aunt, there's little else that can be provided. Will that suffice?

TIA!