3 is indeed the title of this Italian film about a menage a trois, set among the nobility in the Tuscany of the 1780s. It is interesting to note that the film's director and star, Christian De Sica, is a son of notable Italian director
Vittorio De Sica (Umberto D, The Garden of the Fitzi-Continis, etc.). Christian's influential family contributed heavily to the making of this film. Baron Jacopo Del Serchio (Christian De Sica) and his wife Chiara (Anna Galiena) are constantly looking for ways to spice up their sexual lives. One of their favored sports is to watch the servants coupling. However, their tranquility is interrupted when a beautiful young man, Leonardo (Paolo Conticini), sets out to bed them both, and succeeds. Their threefold joining is not a problem, but Leonardo's greater affection for Chiara is, as it leads to the bisexual Baron being jealous of them both. ~ Clarke Fountain, All Movie Guide