No, they have not really sung together for many years, having divorced in the mid 70s, but both are still active as separate acts. Check this site for lots of info on Ian Tyson. HTTP://www.nucleus.com/~cowboy/IanTyson.html

Sylvia Tyson sings as part of the group Quartette, as well as as a solo act. This page gives information about her. http://www.quartette.com/~quartett/

Multi-searches like Dogpile will no doubt turn up even more information on them.