The 43-year-old appeared virtually before a judge ... after he was hit with two charges of death by auto following allegations he drunkenly slammed his Jeep Grand Cherokee into the backs of the Gaudreaus on Thursday night while they were biking on a small roadway in Oldmans Township.

Wearing an anti-suicide smock -- Higgins initially didn't speak much at the hearing ... although when he was informed he would remain behind bars until at least next Thursday -- he seemed dejected.

He leaned back in his chair, closed his eyes ... and then let out a big breath.

The judge told Higgins he was required to remain incarcerated 'til late next week ... because prosecutors have filed a motion for his pre-trial detention.

"The statutes and court rules require me to hold you over for a minimum 72 hours before your hearing," the judge told him. "Because we have a weekend and a Monday holiday, 72 hours becomes Thursday."

Higgins could be seen on camera then shaking his head that he understood.

At the hearing, Higgins also made it known he intends to hire a private attorney to represent him in the case. He was then given instructions on how best to go about that process from a cell.

He was eventually excused from the proceedings after informing the judge he had no further questions.

As we reported, cops say Higgins admitted to drinking "5-6 beers" before getting into the accident.

Johnny and Matthew had been in town to celebrate their sister's wedding, which was slated to happen on Friday -- but was canceled following the tragedy.

Johnny was 31 years old. Matthew was just 29.