Mr Laundrie is the only suspect in Ms Petito’s murder but has been missing for three weeks.
“If you really loved her, you should turn yourself in,” the family said in an interview with Dr Phil.
“You are only making it worse, for us and for yourself.” “For us and for yourself and your family. Let us have some closure. Let us move on and be able to remember Gabby for all the wonderful memories we had with her. Turn yourself in.”
In the same interview, father Joe Petito called the entire Laundrie family “cowards” as the search for Brian continues.
Laundrie, 23, is the subject of a nationwide manhunt following the death of Gabby, whose body was found in Wyoming last month. Authorities say Gabby died by homicide but have not yet released a cause of death. Laundrie has been named as a person of interest in the case, but not a suspect.
Laundrie is also wanted by FBI on an active warrant issued in late September on suspicion of unauthorized use of a debit card.
If you have information on this case, call 1-800-CALL-FBI (225-5324).