In context, the good which the Father will give to his children is the wisdom to deal with the failings of a brother in a gentle manner. In a parallel passage in the Gospel of Luke we are told that the good which the Father gives to his children is the gift of the Holy Spirit (Luke 11:13).1
11 If you then, who are evil, know how to give good gifts to your children, how much more will your Father who is in heaven give good things to those who ask him!