I got a quick response! Over on the fRoots Forum, Ian Anderson showed this to NANCY WALLACE, nominee at this year's folk awards and she said, "Oh my God it's Ma and Pa! And uncle Dom!

This makes it DOM BONITO, DON WALLACE and MAUREEN WALLACE (though she was Maureen Seaton at the time of this photo. She died about 18 months ago) They performed together as THE NORTH WEST THREE.