Your husband is only able to sponsor you and your dependent children ("dependent" as defined by the
IRPA Regulations). He is not eligible to sponsor your extended family - so they are not included on IMM0008. You are the principle applicant on Form IMM0008, and your dependent children (if you have any) are included also - whether they are immigrating to Canada or not. Nobody else goes on IMM0008, or on his form IMM1344A.
Your parents and siblings will be included, however, in the Additional Family Information form (IMM5406) - not because they are part of
this application, but because once you become a permanent resident, they may at some point be eligible to be sponsored by
you, so you have to disclose them.