Should I include both my paternal and maternal grandmothers in Matru Navami Shradh?

Yes, it is traditional and spiritually meritorious to include all deceased grandmothers in Matru Navami Shradh. The sankalpa covers your mother, paternal grandmother (Pitamahi), paternal great-grandmother (Prapitamahi), maternal grandmother (Matamahi), and maternal great-grandmother (Prapitamahi on the maternal side). Including all female ancestors who died as married women within the Matru Navami ritual is considered the most complete form of this observance.