Family is unwilling to give me a death certificate

Location: Auburn, Ca. My mom is in memory care so she is unable to give me the info I need. Her long -term boyfriend ( 15 yr) may be considered common law spouse. The boyfriend was hit in my mom’s car head on and he was killed 3 weeks ago. I live in Washington and have met his children, all adults one time, years ago. Mom and partner have a policy if one passes, the house goes to the other. So, I need access to my mom’s accounts to pay for her care, house payment, bills…. I have a copy that is notarized that in the case of death of him, I have Power of Attorney for my mom. The problem is the death certificate that I need to show that I am the P.O.A.Her children are unwilling to give me one of the original death certificates they have. I told them I can order my own if they will give me info. I need to do that. I have called and texted me to get it but they blow me off. They can’t deal with it because of their grief, it isn’t a good time… All during the time bills are piling up and I am at their mercy. I just need things like D.O.B, date of death, maiden name, drivers license number. What are my options legally?

Author: Zealousideal-Cup8502