Larger families/siblings have been interesting to me in cases like this for some times now..I am an only child so never had this problem dealing with my elderly parents but my husbands family(10 kids) has been another story altogether..
It seems to me that there has to be one of two in every bunch..that for whatever reason, just won't and don't help with anything..if they do show up for a visit in a hospital, etc..it's almost like we should all be honored at their presence?
My husband has such anger and resentment at one of his older brothers for neglecting his father when he was ill and dying, that I dread an altercation..he has promised to stifle any feelings until his mother passes on, then he says it's going to come to a head and he's going to tell him in no uncertain terms what his behaviour did to his parents..it did and does bother them that he neglected them..
I'm not sure this is the way to handle it..I sort of agree with some of the other posters..to just be thankful "you" were there for them..but I guess it's a matter of what each individual feels comfortable with?
take care of yourself..your mom was so lucky to have someone like you...