Letter for any dependent not traveling to UK

[firoz365]

Hi All,
I am in UK on tier 1 and I'm inviting my parents to visit UK as general visitor .
Following are my queries -
1. I have a younger brother aged 16 who is dependent on my parents. He is not traveling with my parents . Do I need a letter from any of my relative confirming that they will take care of my brother back in India during my parents' visit? If yes , where can I get the format or content of the letter.

2. I do not have any utility bill except council tax. Also I am submitting NOC from house agent and rent contract. Is that enough?

3. I am showing my 6 month salary slip and bank statement. 3 months ago I was working with different company so salary slips are from different companies. Is that OK? Do I need any letter from my employer confirming I work with them and I am a full time employee?

Many Many Thanks In Advance To All You Very Helpful People