Answer:
The percentage of students in Kiri's brother's class who think aliens exist is 11/25 = 44%.
Since the number of students in Kiri's class is not given, it's not possible to compare the percentage of students in Kiri's class who think aliens exist to the percentage in her brother's class. We need to know the number of students in Kiri's class and the number of students who believe in aliens in order to compare the percentages.