我弟弟擅长游泳 英语咋说？

应该是my younger brother is good at swimming .
很简单的 要是有不会的你直接问老师吧

my younger brother is good at swimming

你用 My younger brother is good at swimming 或者 My younger brother do well in swimming .应该都可以哦

My brother is good at swimming

My brother is good at swimming

My younger brother is good at swimming.