The Idea Factory - Tales of the Time Traveling Twelve Year Olds

One can see the future. One can travel to the past. Both try to save the same old woman, who ends up dying in the end from old age. When they each succeed as saving her from one of her fates, they get matching marks on their arms of a tree. When one touches the other's, they flick through time, out of either of their control.

A middle grade series, that will be after Cary Simms is finished.