Colin Kaepernick is sitting alone, without even the company or support of the woman who gave birth to him.

Heidi Russo, the birth mother of the 49ers quarterback who has been refusing to stand for the national anthem, told Kaepernick — publicly, on Twitter — he is bringing shame to the family and the country.

Russo, who gave birth at 19 and, destitute at the time, placed him up for adoption, was loud in her disapproval, telling Kaepernick — whose biological father is black — there are better ways to protest what he identifies as oppression of black people and minorities in the United States.

As the Twitter vitriol built, many took shots at Russo for giving up her son, then scolding him from afar. She got a taste of the polarity of Kaepernick’s position and switched to the defensive, alluding to those who “sit on social media in their glass houses throwing stones.” The irony of using social media to criticize her son, then complaining about those who criticize on social media appeared to be lost on her.

Kaepernick has not responded to Russo on Twitter. His social media have gone silent since last weekend, when the world learned of his silent protest.

The specifics on the relationship between Kaepernick and his birth mother are unclear. For years, he said he had no interest in meeting her, even as she reached out repeatedly.

In 2013, ESPN chronicled Russo’s search for a reunion with the son who turned into a multimillionaire NFL quarterback. Kaepernick was adopted by a Wisconsin couple with two kids.

Asked by ESPN whether he was curious about meeting his birth parents, he said no.

“It’s not really a respect thing,” Kaepernick said at the time. “It’s just — [my adopted family is] my family. That’s it.”

Some football fans were so outraged by Kaepernick that they burned his jersey: