Hi bluebird
my sympathy to all your family,My partner has mm,and it is hard to deal with,IT is rare only 3000 cases a year in Britain most doctors will only come across it once or twice in there working lives.the symptoms can be many illnesses,only bone marrow test will confirm 100% that it is mm.
Most people put it down to back problems,age related illnesses,I could go on with many more general problems.You will get over the anger,it is part of the grieving process,no one wants to loose someone they love.So take time to grieve for your brother.