J. Nicholas Shriver Jr., 63, a partner in the Baltimore law firm of Ober, Grimes and Shriver, died Tuesday at Union Memorial Hospital in Baltimore following surgery.

Associated with the firm, once known as Cross and Shriver, since the mid-1930s, Mr. Shriver was president of the American College of probate Counsel and formerly was head of the section on real property, probate and trust law of the American Bar Association.

Born in Union Mills, Md., he was a graduate of Georgetown University and its law school. He was a member of the D.C. Maryland bars.

Durging World War II, he served as an officer in the Army's Judge Advocate General's Corps.

Mr. Shiver belonged to the Baltimore and Maryland Bar associations and was a fellow of the Maryland Bar Foundation and a member of the Maryland Law Institute.

He is survived by his wife, Melanie Dugan Shriver, of the home in Owings Mills; two daughters, Melanie Donnelly, of Owings Mills, and Elizabeth L. Shiver, of Washington; his mother, Mary K. Shriver, of Townson; three sisters, Mrs. R. Styvesant Pierrepont, of Locust Valeey, N.Y., Mrs. Frank McTerran, of San Francisco, and Mrs. Edward L. Koch, of Littleton, Colo., and two grandchildren.