Midfielder is unhappy that his brother, who is suspended after failing a drug test, cannot feature at Wembley, but wants to make amends by winning the cup for him
The Ivorian centre-half was suspended in March for failing a drug test, and has been unavailable for City since.
But the Eastlands club have made their way to the final of the domestic cup competition in the absence of the former Arsenal defender, and could potentially end their wait for silverware - which stretches well over three decades - on Saturday.
"There will be sadness," Toure, the former Barcelona midfielder, told reporters.
"Before I signed for City I told my brother I wanted to come to England to play with him, and to win something together.
"That won't happen tomorrow, which means it will be a hard moment for him, and for me as well.
"We have spoken about the best way of getting round the problem and decided it is by winning the cup.
"He is supporting me and if we win, it will be for him as well."