Ben Affleck Will 'Always Want the Best For' Jennifer Garner, Who's Newly Dating CEO John Miller

Three weeks after finalizing her divorce from Ben Affleck, Jennifer Garner has a new beau, businessman John Miller

Three weeks after finalizing her divorce from Ben Affleck, Jennifer Garner has a new beau, businessman John Miller.

And Affleck supports his ex —with whom he shares daughters Violet, 12, Serpahina, 9, and son Samuel, 6 — moving on.

“Ben will always want the best for Jen,” an Affleck friend tells PEOPLE. “They continue to have a really strong relationship and both work very hard to make everything easy for the kids. She has always been supportive of him.”

Since announcing their plans to divorce in June 2015, Affleck, 46, has dated Saturday Night Live producer Lindsay Shookus and Playboy model Shauna Sexton, and he and Garner have continued to co-parent their three children.

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Garner, 46, also stood by Affleck when he entered treatment for alcohol addiction for the third time in August, driving him to a Malibu treatment facility and visiting the actor during his stay.

While she’s been ready to find love again, Garner wanted to wait until her divorce was finalized to start dating.

RELATED VIDEO: Ben Affleck Reveals He Completed 40-Day Rehab Stay: ‘I Am Fighting for Myself and My Family’

“Jen has been wanting to move on and now when the divorce is finalized, she finally can,” a source said earlier this month. “She has had no choice but to be patient since Ben needed to finish his rehab treatment. But she was ready to sign the papers.”

FilmMagic; Ringo Chiu/ZUMA Wire

Now Garner is taking things slow with Cali Group CEO and chairman Miller, 40. “They are casually dating, but it’s not serious,” another insider says. “He hasn’t met her kids.”

• Reporting by LIZ McNEIL