|I have grapes and the fruits are uneven in size. Some are big and the others are still unripened in the same cluster.
|Your grape clusters were inadequately pollinated. There's not much you can do about this except to encourage lots of bees and wasps to visit your garden. If you have lots of flowers in bloom at the same time your grapes are blooming, you'll probably have better pollination and fuller clusters.
Best wishes with your grapes.