Hi! Is there such a class in boost? What I'm thinking of is fairly simple, it could be written easily with type_traits and mpl::if_, but I prefer using the standard boost components, if they exist. select_parent<T1, T2>::type is a) T1 if T1 is T2's (direct or indirect) parent b) T2 if it is the other way round c) T1 if T1 and T2 are the same d) and generates some compiler error if T1 and T2 are not related at all. Thx, Agoston