WASHINGTON — Three more people have been charged in connection with the case of two Montgomery County sisters who disappeared in 1975.

Leslie Engleking was charged with perjury and Amy Welch and Gladys Stangee were charged with obstruction of justice in the case of the rape and murder of 12-year old Sheila Lyon and her sister, 10-year-old Katherine Lyon. All three have posted bond.

The three are all related to Richard Welch, who is being looked at as a person of interest in the disappearance of the two girls. Engleking is Welch’s brother-in-law, Amy Welch is his granddaughter, and Stangee is his sister, The Washington Post reports.

Montgomery County police are working in conjunction with Bedford County law enforcement to investigate the disappearance of the sisters who were last seen in 1975 at Wheaton Plaza, which is now known as Westfield Wheaton Mall.

Patricia Welch, who is married to Richard Welch, was formally charged with perjury for lying to the jury in December. His nephew Lloyd Lee Welch, was charged with first-degree murder in July for the girls’ deaths.

The special grand jury was first impaneled in October to assist investigators.