A source tells ET that, after the couple decided to slow things down a few months ago, they have been wanting to spend more time together as of late.
"In March, Jen and John decided to slow things down a bit. Jen was focusing on the kids, her career, and co-parenting with Ben [Affleck]," the source says, adding that "Jen and John are so compatible."
"They have great chemistry and truly love each other’s company," the source says. "In the last couple of months, while they have taken a little time for themselves, they have missed each other and both realized they wanted to spend more time together."
As they spend more time together, the source says, "Jen wants to continue to explore their relationship and see if John is the right one for her."
"John adores her and he is comfortable with her celebrity status, which is a relief for her," the source says. "Jen’s friends are encouraging her to spend more time with John. They think he seems to be the obvious next step in her life."
Back in October, a source told ET that Garner and Miller, a businessman, had been dating for a few months. The news came just weeks after Garner and Affleck finalized their divorce after more than three years of separation.
In January, a source told ET that "Jen has something very different with John than she had with Ben."
"She and John are both interested in living a healthy lifestyle, working out and eating well, except for the occasional trip to Chick-fil-A! When they aren't with the kids, they take time on their own seeing movies and having romantic dinners," the source said of the couple's combined four children. "They've already taken the kids to the mountains together, and Jen's friends describe John as a mountain man. He loves to do outdoorsy things."