To support a group of mobile sinks in wireless sensor networks, region-based routing protocols by using a single entity nature have been proposed. They periodically register the region location information of the mobile sink group and exploit flooding for the data delivery within the region. However, they have a data delivery failure problem for some sinks due to the asynchrony between the registered region and the actual region of the mobile sink group due to its mobility. They also have an excessive energy consumption problem due to flooding data within the region. Thus, to solve the data delivery failure and the excessive energy consumption problems, we propose a routing protocol for a mobile sink group by utilizing its movement pattern which has a slow variance and continuous stream i.e. moving properties. In the proposed protocol, a source sends its data only to sensor nodes on a line that a mobile sink group potentially passes, and mobile sinks get the data from the line when they pass it. Simulation results show that the proposed protocol has better performance than the existing protocols.