To address the issue:
1. Take the initiative, schedule a weekly or biweekly status meeting with all three of you, prepare the status summary prior to the meeting, if he likes, the two of you could take turns to draft such summary reports and review prior to meetings.
2. Be very clear with your coworker, that you don't feel comfortable that he send out summaries without you reviewing it, it should be a joint effort. This way, he knows your boundry and if he continues to cross the line, escalade it.
