Celeste Rivas's family is reportedly planning to release a statement through their attorney on Monday in reaction to D4vd being arrested 7 months after the 14-year-old's decomposing body was found in the trunk of his Tesla.

The family statement would be the first time the public hears from Celeste's loved ones since D4vd's Thursday arrest in Los Angeles.

Prosecutors have a Monday deadline to either charge D4vd with a crime or release him from police custody ... and, according to ABC7, an attorney representing Celeste's family says if the Los Angeles County District Attorney holds a press conference, Celeste's parents and sister will be there.

The family lawyer also says Celeste's relatives plan to attend a potential D4vd arraignment next week ... should prosecutors indeed file criminal charges.

LAPD arrested D4vd Thursday ... and Mark Geragos said on the "2 Angry Men" podcast cops took the law into their own hands because they were tired of waiting for the D.A. to file charges.

One high-ranking LAPD source told us the Los Angeles County Medical Examiner determined the manner of death was homicide ... and it sounds like police were waiting for that official declaration before making their move.

Attorneys for D4vd -- real name David Burke -- told TMZ ... "Let us be clear - the actual evidence in this case will show that David Burke did not murder Celeste Rivas Hernandez and he was not the cause of her death."