Do you have family in the UK

Hi everyone,

I was just reviewing my online visa application form, which i submitted last week, and there was a question "Do you have any family in UK?" and the examples of family written below that questions included spouse, parents, partners, grandparents and grand children but not siblings. I do have a sister living in UK with her family from last year or so and they all have Italian passports. Should I have mentioned her and if yes, should I withdraw my application and submit a new one?

One of my ex work fellows who is on tier-2 visa in UK these days suggested to write down a letter informing UKVI about the error and reasons for making that mistake. (Siblings wasn't mentioned in included family in main screen). Should I send them email on paid inquires attaching my letter explaining the reasons or I have to withdraw my application altogether? Any help would be greatly appreciated