Appling under family member - unmarried to my mother

Hi,

Thanks for taking the time to read, I have a strange question.

I would like to apply for PR for years 2006 - 2011 when I lived with my mum and her unmarried partner (in a way my step dad) (I was 12 at the time)
Will he count as a family member sponsor? (he's not my biological father, and he's not married to my mum).

My mum currently does not hold PR and next month could apply her self for 2012-2017

I can not apply for any years between 2012 and 2016 as I was a student without CSI... so this is my last chance!

Thanks for all advice!

Adam