where's和where are的不同?请举例说明用法的不同

where's 后接第三人称单数形式名称或代词,where are 后接第二人称和复数形式名称或代词,e.g.
Where's the boy?
Where's my pen?
Where's your brother?
Where are you from?
Where are the girls who were here just now?
Where are the apple that in the basket yesterday?