The instruction GUIDE states: This form must be completed by:
•You, as the principal applicant,
•Your spouse or common-law partner (whether accompanying you to Canada or not), and
•Your dependent children aged 18 or over (whether accompanying you to Canada or not)
If you are single, there would only be ONE copy to fill - your own.
If in a relationship, your partner/spouse would ALSO fill out their OWN copy with THEIR personal name as Applicant, you as spouse, THEIR brothers and sisters names, their parents, etc
If children over 18, they will complete THEIR OWN copy
I hope Dr H will back me up on this, but I know this question has come up before. You can also do a SEARCH on the main forum page, top right corner. All the best.