Blake Lively's brother-in-law defends her amid the drama “It Ends With Us”

Blake Lively's brother-in-law Bart Johnson defends her in light of the controversy surrounding her film It ends with us.

Johnson, who is married to Blake's sister Robyn Lively, posted a birthday message to 37-year-old Blake on Instagram. High School Musical Actor Johnson later responded to a commenter who found it “disappointing” that Blake seemed to “promote happiness in an environment of domestic violence, with no regard for the victims.”

“I'm really sorry you feel this way. I'm sure you have a big heart and want the best. I can promise you the truth has not come out yet,” Johnson, 53, wrote in response to the comment. “Blake worked harder on this film than anything I've seen her do my entire life. Because it meant so much to her.”

Blake, who is also a producer on the film, plays the role of Lily Bloom in the adaptation of Colleen Hoover's novel. The story deals with toxic relationships, domestic violence and other complex issues. There are also reports of tension between Blake and her co-star and director Justin Baldoni.

Johnson added in his comment: “The message is in the book. And the movie. Not in short clips/interviews,” he added in the comment. “It's the reason the message/this movie/ resonates. Were mistakes made? Yes. I make mistakes in life. But they are not scrutinized. Either way, I respect your views. I have nothing but love for you.”

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Regarding the tension between Blake and Baldoni, 40, a source told PEOPLE on August 13 that the behind-the-scenes issues are about more than alleged creative differences between the two.

“Everything is not as it seems,” said a source on the set at the time. “There is much more to this story. The main actors and Colleen Hoover wants nothing to do with him.”

In a message to It ends with usOn opening weekend, Lively thanked her fans in her Instagram story and shared resources to support victims of domestic violence.

“It ends with us is a story about women's experiences. All the highs and lows. And we are so proud of it,” she wrote at the time. “We celebrated this film and brought such an important message to the masses. Thank you to everyone who embraced it so much. It ends with us with the same love, pain and joy that we felt when we shared it with all of you.”

Johnson's birthday post for Blake included a series of photos of the two together from years past. In the caption to his post, he explained that he and Blake met after Blake's father, the late Ernie Lively, hired him to teach an acting class for teens.

“Tonnes of stories of family trips and vacations, chaperoning her school trips and MOST IMPORTANTLY, helping me win the favor of her older sister Robyn (now my wife of 25 years) who didn't know I existed for years after she met Blake!!,” he wrote in his caption. “For 30 years I was privileged to be friends with this kind, loving, dedicated, hard working and inspiring strong woman. [woman]!!”

Robyn, 52, called Blake “one of the best people I know” in an Instagram tribute for her birthday. She also responded to a commenter who seemed to address the controversy: “Blake is a lovely human being!! I hope she knows that the crowd of people who love her is so much bigger than the negative voices. Happy birthday Blake!!” Robyn wrote back: “Thank you for this.”