Justine Wilson, a novelist who was married to Elon from 2000 to 2008, weighed in on Vivian's legal filing to have her gender identity changed to female, and to change her full name ... including dropping her dad's famous last name.

She tweeted a convo she recently had with one of her children, and while Vivian has a twin brother, Griffin, the timing makes it pretty clear this was a chat with Vivian.

Justine says her 18-year-old said, "I can't believe I'm as normal-seeming as I am," after having what she calls a "weird childhood." Justine replied, "I'm very proud of you," to which Vivian said, "I'm proud of myself!"

The proud mother's tweet dropped right after the story broke about Vivian's desire to change her name to Vivian Jenna Wilson. What's interesting about Justine's very public support is that Vivian's made it clear she's got beef with Elon.

In the docs she says, "I no longer live with or wish to be related to my biological father in any way, shape or form."

Neither Elon nor Vivian previously said anything publicly about their relationship or her transition ... but back in December 2020, Elon tweeted he supports the transgender community, but added ... "All these pronouns are an esthetic nightmare."