Not sure what you mean by struct, but you just need to fill out a family pooling form and write the relationship to account member.
when I try to apply online it states "Step 2: Attach Proof of Relationship
To verify your relationship, attach a visual copy of any one of the following documents: family register, resident registration, household register, marriage certificate, birth certificate or tax return."
That's what I mean by strict?? is that necessary or can I just send the family registration doc? they say they need proof of relationship? whats good enough?