用简单的英语解释下列句子:how old is you brother

这是个问句，英语的解释当然也要是问句,如下：
What is brother's age?

the question is asking the age of your big/small bother

直译是--兄弟 怎么老是你

翻译是--你兄弟（哥哥，弟弟）多大了。

用英语解释-- It means what ages of your brother.

what is the age of your brother?

how old is used to ask the age of some.
your brother is the target of question or the one asked.
is is the connector which combine two parts together