please help! Use Of Family Member Representative

[supreme]

Hi,

I'm representing my mother and brother for a visitor visa to Canada. We have signed IMM5476E. But there is another form IMM5713E which is another use of family member representative form.

So my brother is over 18. And I guess the purpose of that document to assign his mother in the form 5713. But in this case I'm representing both of them and it's not clear what should I fill out?

Thanks in advance. I hope I'll finish this process one day.