To jest nie fair wobec twojego brata (why the word FAIR ?) The translation would it be not instead : To nieuczciwe wobec swojego brata ?
Thank you for your advice
Tak jest swojego rodzaju zapozyczone słowo " fair play" i znaczy to to samo co “nieczysta gra”, “nie uczciwe zagrywki” itp…
You can say it as a " Its not going to be cool because this person always has been for you like a brother, it’s better to play fair"
Eduard.