Kansas in August

From Amazon.com:

A toe-tapping story of life and its wonderful and unexpected complexities. Hilary is a young, attractive teacher with aspirations to be a tap-dancer. Henry, his elder sister, is a crisp, professional psychologist. The unpredictable and unreliable Rufus, a failed pianist, is their lover - whom neither Hilary nor Henry realise they are sharing. Despite the constant danger of discovery, this unwitting triangle persists, in delicate balance - until, that is, someone new and totally unexpected enters the frame. Having rescued an abandoned baby boy, found soaked and tearful in a subway, Hilary decides, to his own great surprise, to become a surrogate parent.