yes, you can if you can show
1. birth certificate of your wife and brother in law have common parents name.
2. your Brother in law, mentioned your wife's name as his family while applying for PR
3. your BIL can provide his Canadian citizenship/PR proof, Income tax returns, utility bills, credit card/bank statements
4. most importantly, you don't get divorced before finalization ( sorry to say this, but have seen such cases on this forum !!)