Many applicants, including myself, have struggled to make sense of the guide to completing this form, which I still find very unclear. It seems to suggest that the sponsor, if he or she is the spouse or CL partner of the applicant, also has to complete a form. That may not be necessary. You may find some further help in this thread:http://www.canadavisa.com/canada-immigration-discussion-board/additional-family-information-imm-5406-question-t123955.0.html When I applied I dealt with the ambiguity by sending two forms, one completed by myself and the other by my CL partner and sponsor, a Canadian citizen. My application ended successfully; so there is something to be said for ignoring the commonly expressed opinion on this forum that only the principal applicant needs to complete a form. If you follow my precedent, the principal applicant's form will contain details of you as his spouse and of his parents and his brothers and sisters, and your separate form will contain details of him as your spouse, your parents and your siblings. I feel sure that there are many members of this forum who disagree with me, but there surely can be no harm in sending two separate forms, one by the principal applicant and another by the sponsoring spouse!