Mr. and Mrs. Bones were a couple killed by Death Eaters in the 1970s (PS4, BN). Either Susan’s grandparents or her aunt and uncle Edgar. When asked in a 2000 interview if the Boneses who were killed were related to Susan, JKR said “They were her grandparents.” Rowling may have later changed the relationship when she wrote book five.
Mr. and Mrs. Bones
First Introduced PS4: The Keeper of the Keys