My favorite story is that Giancana sent Roselli and another guy to talk to Joe about calling the boys off because they had helped him win the WVA primary and Chicago. Joe said he would talk to them when the family got together at Christmas. In the meantime Joe had the massive stroke and the conservation supposedly did not take place.
The Giancana-Daley-Kennedy-Sinatra quadrangle relationship is well documented. Throw in Marilyn Monroe for the icing on the cake.