With baby number three on the way, Mark Wahlberg is committed to making his family life as successful as his film career – and that includes marrying longtime girlfriend Rhea Durham.

"We continue to grow in our relationship," Wahlberg told PEOPLE on Thursday at San Diego's Comic-Con International, where he was promoting his upcoming film Max Payne. "I think we have a much better chance at succeeding and staying together."

The 37-year-old actor and longtime girlfriend Durham, 30, plan to have a formal wedding next summer after their baby is born. By Scott Huver@ People.com