The boy whose mother is a painter is good at drawing
母亲是画家的那个小男孩擅长画画.为何有2个be 动词?这是一个复合句，包括一个主句，一个从句。The boy ... is good at drawing 是主句，whose mother is a painter 是从句。主句和从句都是相对独立的句子，所以，可以有两个be，不懂再问