Blood Brothers is the 10th episode of NCIS Season 13 and also the 292nd episode of the entire NCIS series.
When his two Marine siblings are killed in the line of duty, the team is tasked to help a sailor battling leukemia locate a potential bone marrow transplant before it's too late while in the aftermath of events in the previous episode, Bishop returns home to Oklahoma to spend Thanksgiving with her family.
- Barbara Bishop and George Bishop, the mother and brother of Eleanor Bishop are both introduced for the first time.
|Leroy Jethro Gibbs||Mark Harmon||Special Agent in charge of the NCIS Major Case Response Team.|
|Anthony DiNozzo Junior||Michael Weatherly||Senior Special Agent and second-in-command of the NCIS Major Case Response Team.|
|Timothy McGee||Sean Murray||Special Agent of the NCIS Major Case Response Team.|
|Abigail Sciuto||Pauley Perrette||Chief Forensic Specialist for the NCIS Major Case Response Team.|
|James Palmer||Brian Dietzen||Assistant Medical Examiner for the NCIS Major Case Response Team.|
|Eleanor Bishop||Emily Wickersham||NCIS Probationary Agent.|
|Leon Vance||Rocky Carroll||Director of NCIS.|
|Donald Mallard||David McCallum||Chief Medical Examiner for the NCIS Major Case Response Team.|
|Tobias Fornell||Joe Spano||A Special Agent with the FBI.|
|Barbara Bishop||Lindsay Wagner||Eleanor Bishop's mother.|
|George Bishop||Ryan Doom||Eleanor Bishop's brother.|
|Paulette Quinn||Patricia Bethune||Alex, Rebecca and Sean Quinn's mother.|
|Sean Quinn||Eric Nelson||The brother of Alex and Rebecca Quinn and son of Paulette Quinn.|
|Alex Quinn||Jack Mikesell||A Lieutenant in the United States Navy and the brother of Sean and Rebecca Quinn and son of Paulette Quinn.|
|Richard Doogan||Grantham Coleman||Former Army Sergeant.|
|Alton Brinkman||Harry Van Gorkum||A man who appears in the episode.|
|Malcolm Turro||Stuart McLean||A man who appears in the episode.|
|Marine (Blood Brothers)||Scott C. Roe||A man who appears in the episode.|