Visitor visa for my mother

[arkadsk]

Hello everyone,
Apologies if this has been asked before but I was looking for help and guidance on what documents to submit for a visa for my mother.
To give a bit of background my mother is widowed and has never worked as she mainly was a housewife. Her current source of income is the monthly returns on investments. She has a couple of them and the payout is regular which is evident on the statements.
Along with the details of the investment, we will be submitting the below documents-

• Application

• Bank Statements with savings of around 3.5k GBP.

• Letter of invitation

• Copy of my biometric card.

My question was what other documents can I submit that confirm strong ties back home. I read somewhere you can submit evidence of family ties, what would I need to submit for that. We have a small family it is only my sister and my uncle back home.