The 27-year-old ended his four-year relationship with Stewart following her fling with director Rupert Sanders in 2012. Contrary to rumours that Pattinson is now romantically involved with Keough, a source says "he doesn't want to be that guy".
"He doesn't want the image of him being that he is stealing the friend in the wake of the relationship with Kristen," femalefirst.co.uk quoted a source as saying.
"Rob did tell people that he reassured her that he wasn't going to date her friends and make things more awkward between them, because the breakup is and has been awkward enough," the source added.
Recent reports hinted that Pattinson went over to Stewart's house over the weekend to collect his stuff.
"Rob initially reached out to Kristen because he wanted to stop by and pick up the rest of his stuff, but apparently he also wanted to see her. He stopped by on the weekend and they both spent some time together, catching up," the source said.
"Kristen was really happy to see him, but I think in the end they were both sad because they still have feelings for each other. It's not as simple as just getting back together. Seeing each other brought up lot stuff for both of them.
"For now, work, not rebuilding a relationship, comes first. It's sad," the source added.