jus sanguinis

This principle of jus sanguinis has deep historical roots both in Canada and internationally, and it is evident from the legislative history of the [Act] that Parliament has always intended the term “parent” to refer to genetic parents for derivative citizenship purposes.

Since the Federal Government is responsible for immigration and the Indian Act, it takes a very different view of "family status" than the Province's do. 

http://www.canlii.org/en/ca/fca/doc/2014/2014fca85/2014fca85.html?searchUrlHash=AAAAAQAjImh1bWFuIHJpZ2h0cyIgK2lsbGVnaXRpbWF0ZSArY2hpbGQAAAAAAQ&resultIndex=8