answer:Having gone to one of the sisters, I can say that there was no official affiliations (due to proximity) except for H & R, C & B. The informal connections were social. At Wellesley, the girls dated men from most of the Ivies – Penn was a far piece, but there were good trains; the ride from Cambridge to Wellesley was 30 minutes. I married two guys from the same class at Harvard, not at the same time, of course. As an undergrad. I dated men from H, Y,P and D. Today MIT is part of the Ivy League, mainly to insure that the Financial aid packages from the 8 schools are the same….no buying of students there.