Timecrack by William Long

"Timecrack" is an exciting sci-fi/fantasy adventure about two young brothers who are swept into a timecrack—a portal that takes them through time and space into a parallel universe. There, the teenagers search for their missing parents, who were taken by a time crack from the archaeological dig, deep in Mexico's Yucatan jungle and pyramid. During their search, the young brothers encounter Anton and his brother—prisoners recently escaped from Mars—who want to kill them. Luckily, they are able to make friends as well, including the Lancers in their flying machines, and the Androts—human-robots who are the protectors of the Amasian cities on New Earth.