Visitor visa- Parent and child

[amanpreet.kaur01]

My sister applied for a a visitor visa from Australia. She put the question answer to if the child is going to accompany she said yes and also started as family application however only one form was submitted at end. Will her child be able to accompany her he is only 5 years old. If yes is there a separate application need to be filed?

 

[amanpreet.kaur01]

Also she can not get consent letter from father what to do