I am good at swimming but my bother was not对吗

I am good at swimming but my bother is not.时态一致比较好

I am good at swimming but my brother not.即可。

这句语法不对称，为什么后半句要用过去时态？
如果按原句翻译，意思是：
我擅长游泳，但我弟弟（哥哥）以前不擅长。
最好把语法改一下，都是一般现在时态。
I am good at swimming ,but my brother is not.

把was not 改为 is not 或 does not 时态不一致

时态不对，但用法是对的。可以写成：I am good at swimming but my brother is not.或者：I am good at swimming but not my brother.