YOU SAID:

my brother got peed on by a bat

INTO JAPANESE

私の兄はバットにおしっこをかけられました

BACK INTO ENGLISH

my brother was peeed on the bat

INTO JAPANESE

私の兄はバットにおしっこをされました

BACK INTO ENGLISH

my brother was pissed on the butt

INTO JAPANESE

私の兄はお尻に腹を立てていました

BACK INTO ENGLISH

my brother was pissed in the ass

INTO JAPANESE

私の兄はお尻に腹を立てていました

BACK INTO ENGLISH

my brother was pissed in the ass