This page ( http://www.lidoriki.com/2012/02/1899_23.html?m=0http://www.lidoriki.com/2012/02/1899_23.html?m=0 )has some old marriage records from the area of Lidoriki, in central Greece. Entry #60 is about the wedding of Maria Karaintros, daughter of Athanasios, from Granitsa to some Leonidas Raptis, son of Christos. She could be your grandfather's sister. There are Karaintros families in the the nearby village of Teichion. They may be related. There is also a very famous composer from that village. Her name is Eleni Karaindrou.