<human>: I'm a 22-year-old college kid, home for the summer with my parents.  My 20-year-old brother is also home for the summer.  He is frequently rude to my parents, and basically balks at the idea of doing anything to help out around the house.  Tonight my mother asked him to mow the lawn, to which he refused, saying that he had already done it enough for the summer and that he shouldn't have to do it any more than once a month (my father works frequently and my mom has severe health problems that make mowing difficult).  When I got tired of his attitude (he does this a lot) and tried to tell him how selfish he was being, he told me "shut the f*ck up.  Don't make me come over there" and tightened his hands into fists.  He has a history of anger issues, and once threatened my dad with a kitchen chair.  Reddit, I'm looking for advice on how to handle these situations, because they're becoming more and more frequent.  I'm thinking he probably needs to see a therapist.  I'm also a little worried about his relationship with his current girlfriend, if this is how he treats his mother and sister.  He usually gets along fine with my dad.  Oh, and my parents do nothing in response to these outbursts.  I think they've given up, and generally just try to appease him.

Can you condense the text into a few key points?
<bot>: My brother is rude to my mother, occasionally rude to me and has threatened physical violence on more than one occasion for being asked to do minor chores around the house.  Looking for advice.