FAIRFAX, Va. — Amber Heard once called Johnny Depp an “old fat man” and questioned why French fashion house Dior would ever want to work with him, the actor’s sister testified on Tuesday.

Christi Dembrowski — the first witness to take the stand in Depp’s bombshell defamation lawsuit against Heard — described the former couple’s volatile relationship, saying she was “devastated” when her younger brother decided to marry the actress.

The Hollywood pair fought often, Dembrowski told the jury, noting that her younger brother’s “standoffish” ex-wife would often deride him.

When Depp told Heard that Dior was interested in a campaign with him, she was “in disbelief and sort of disgusted,” the sister claimed.

“Dior, why would Dior want to do business with you? They’re about class and style, and you don’t have style,” Heard allegedly said.

Dembrowski, 61, who helped manage her brother’s career, said she would book an extra hotel room when the couple traveled together for Depp to use in case he and Heard fought.

When asked about her reaction to their decision to get married, Dembrowski replied: “I was scared, I was devastated actually.”

“I actually tried to talk him into talking waiting a bit longer,” she added.

The “Aquaman” actress refused to sign a prenup, according to Dembrowski. The sister’s claim refutes claims by Heard’s defense attorneys that it was Depp who decided to forgo a prenup.

During cross examination, Heard’s lawyers grilled Dembrowski about her brother’s drug use, presenting her with text messages she sent him in February 2014 urging him to “stop drinking,” “stop coke” and “stop pills.”

Dembrowski said she couldn’t recall the context, and wasn’t able to confirm that she was telling her brother to stop doing cocaine in the message.

“I understand the words were there I don’t recall the timing,” she said. “I probably was not joking but maybe I was repeating what something else told me to write.”

Depp’s team had Dembrowski speak at length about their upbringing and their mother, who she said was physically and emotionally abusive. She told the jury that Depp never hit their mom, and that he would often just leave the room.

At the center of the trial is a 2018 Washington Post op-ed that Heard, 35, wrote where she called herself a victim of “sexual violence.”

While Depp wasn’t named in the op-ed, the actor claims it ruined his reputation and career after it was widely assumed Heard was writing about their five-year relationship. He is suing Heard for $50 million in damages.

“I believe there is a negative effect on anyone’s career when there are accusations as there have been,” Dembrowski said when asked about the piece. “Personally, I know he doesn’t want people to feel … that he could ever be that type of person, which he isn’t.”

She says “the part that bothers him the most” is that the abuse allegations “trickle down to his children.”

When his sister spoke about abuse, Depp, 58, looked solemn. Throughout her testimony, the three-time Oscar nominated actor swirled in his chair, was seen holding back tears, closing his eyes at certain points and looking down into his lap.

Dembrowski is set to be back on the stand Wednesday.

The trial is expected to last more than a month and include testimony from both Heard and Depp and a string of other high-profile names, including Elon Musk and James Franco.