Visitor visa for kids only

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Hi 

I have a query, I hold visitor visa for 10 years, my kids 10 years & 16 years want to apply for visitor visa. For 10 year old kid will be drop-box but 16 year old kid needs to go for visa interview. 

Can I apply visitor visa only for kids and what is the possibility for approval. Do I need to carry any additional documentation. 

My brother lives in USA and my parents also have valid visitor visa, can i apply visa for my kids only or they need to accompany with someone during interview. 

 

Thanks