How to get ova ur ex bf..?

well i need help.. i was wit this boy.. n i saw him making out with my sis @ the mall. but when i told him i saw him he was lieing so i broke up with him.. but now he keeps texing me n calling me... wat shuld i do. go bac out wti him or dont do nothin... p.s i rly like his bro,,, wat shuld i do... HELP ME!! =[