译成英语:穿着运动服的两个也是我的堂兄弟.

堂兄弟当然是cousin，怎么变成brother-in-law了？
The two guys in sport suits are also my cousins.

The two guys in sport suits are also my brothers-in-law

The two who wear sport suits are my brother-in-law too.

The two people in the tracksuit are my cousins too.

The two in sportswears are both my cousins.

The two boys dressed in gym outfits are also my cusins.