According to the news source, the engagement news comes nearly two years after the couple began dating.
"We share the same values," the Ugly Truth star told Us at the Riverkeeper Fishermen's Ball in NYC last month. "Family first ... We like to have a good time and work hard."
Hines, 48, has been married once before, while this will mark wedding No. 3 for Kennedy Jr., 60.
The two have also been seen promoting each other's causes.
"It's fun to have a partner," she explained to Us in April. "He's so dedicated to the environment and clean water, so we take turns. He'll come to my United Cerebral Palsy event and walk the red carpet with me. It's a good match up."