I have added my half brother for the 15pts as he is a pr. My issue is that our father’s name is not on either of our birth certificates, how else can i show proof of relationship?
Sounds like you are out of luck. Why would you claim points when you can't prove relationship? You knew your dad wasn't on your certificate, so even if he was on your brother's that still doesn't prove relations. But now, none of you don't have his name on the certificate.
"...Proof of the relationship of the applicant or the accompanying spouse or common-law partner to the family member must also be provided (e.g., a birth certificate, an official document naming the applicant as a relative, a copy of the inside back cover of the relative’s passport showing the relative’s parents’ marriage certificate, legal adoption documents and any other documents that prove or describe the relationship)..."