How can I get the records of beneficiary changes near death on my deceased brothers pension and life insurance?

My unmarried,childless brother passed away in Ca. June 2017. In Feb 2017,4 months prior to his death (dying of kidney and liver failure) he called me and said I would be receiving the lion's share of his near 1 million dollars pension and life insurance when he passed. It turns out that our youngest brother (who was his caregiver right at the end) magically ended up with apx.1.2 million dollars,including life insurance,pension,house,savings etc. The circumstances have all the hallmarks of "undue influence" Our parents are still living,Deceased brother had a will and trust. The records I am interested in seeing are strictly as mentioned in the question. Can records be made available without litigating?