x => x.Child.GrandChild1
x => x.Child.GrandChild2Collection.SubInclude(c => c.GreatGrandChild)
var queryOver = session.QueryOver<T>().Where( ...expression to select root objects... );
for every subpath in the current expression:
queryOver.RootCriteria.SetFetchMode(subPath, FetchMode.Eager)
queryOver.RootCriteria
.SetResultTransformer(new DistinctRootEntityResultTransformer())
queryOver.Future()