Dr. Brian Evans and Dr. Susan Evans

Dr. Brian Evans and Dr. Susan Evans

*Oh boy. No matter how you slice it, this is not a good look.

Two prominent doctors once featured on the show “Dr. 90210″ are involved in a nasty child custody war.

Apparently, the eldest son of plastic surgeon Dr. Brian Evans and dermatologist Dr. Susan Evans has accused his father of sexually abusing his younger siblings. TMZ has learned that the three younger kids will now be separated from their older brother.

According to a request for a temporary restraining order/TRO, filed by Brian and Susan’s 12-year-old son on Oct. 15 … Brian touched his 6-year-old son’s penis — and also touched the genitals of their 8-year-old twin daughters.

Further, the eldest son claims Brian “hit me in the face, dragged me for 2 rooms” and threatened to kill the kids and their mom. According to the TRO request, this went down in Oct. 2012 … a full year before the TRO was filed.

Brian Evans’ attorneys adamantly deny the accusations and say that they have been investigated and disproved by authorities.

The court previously issued a major modification of child custody, which granted Brian legal custody of all 4 children, and physical custody of the three youngest ones. The hand-off was scheduled for this past Friday morning in L.A. County Family court.

The order also prohibits Susan from having any contact — “in person, by telephone, text, email, or otherwise” — with the 3 kids for the next 30 days. The oldest son will continue living with Susan.