We have to wait a long time for hot water to arrive at our kitchen sink. A near by bathroom sink does not have the time lag that the kitchen does. Could the dishwasher next to the kitchen sink have something to do with this situation?

Probably not if its plumbed correctly. The rooms may be close together but that does not mean the piping is equal in length. You can always add on a recirculation system like D'Mand Tankless Water Heaters and D'MAND Systems just ignore the tankless ad and read about D'mand