Why are there five people in the band, Westlife and girlhood? Tell me why.

They are a group, not a band, LZ should be clearly distinguished. Generally, band members have a division of labor, such as lead guitarist, drummer, keyboard player and so on. And don't compare girlhood with Westlife. There are as many bands as you want. There is only one person in Owl City, but Owl City is a band. There are six people in Linkin Park. There are only four greatest Beatles. There are not enough musicians, but the number of bands is still the same.