How do I claim a 401k that belongs to my brother who has last over 10 years now. I wouldn't even know where to look for it except that it was in California. I am his only living sinking as our other siblings have passed as well along with our parents bel. (personal info removed)

Do you know where he worked? You can try contacting the PBGC Pension Benefit Guaranty Corp - PBGC Protects America's Pensions

It's your belief that he would have named you as his beneficiary since he was not married, had no children, no living parents, and no other living siblings when he died? And did you mean to say that your brorher died over ten years ago? If so - whoever handled his estate affairs back then should have notified the 401(k) administrator about his death and the account would have been transferred to the named beneficiary on the account.