If you are talking about a Master/Slave or Parent/Child setup, perhaps Peter will know more about that when he wakes up here in a few hours.
But one thing I know for certain is that you will see repeated rows if you have defined a Master Page with breadcrumbs in it as well as having breadcrumbs enabled in the Single Source Layout properties. If that's the case, you typically need to turn them off in the Single Source Layout recipe.
Thanks for your help. When I looked at the child projects they were displaying one line so I remerged them into the parent project and the issue is resolved.