In 1960, Haines married painter Adrienne Rappaport, who used the name Adrian Rappin professionally. They had one daughter, Avril Haines, an attorney who is serving as the current Director of National Intelligence in the Biden administration. Rappaport died in 1985 after developing chronic obstructive pulmonary disease and later contracting avian tuberculosis.
In 1986, Haines married his current wife, economist [http://www.mcleveland.org/ Mary "Polly" Cleveland].
In 1964, Haines and Rappaport purchased two small run-down rent-controlled apartment buildings on New York's Upper West Side for $140,000, $10,000 down and for a time employed Al Pacino as the building superintendent.
When Haines and Cleveland sold the buildings for many millions of dollars in 2009, they put half the net proceeds into a foundation for the benefit of scientific and economic education.