The Days of Our Lives actor praised his daughter's boyfriend at the launch of Loukoumi's Celebrity Cookbook at LA's Treehouse Social Club.
"He's a charming young man," the soap veteran told Us Weekly. "I think they make a wonderful couple."
John said that he and his wife "get together whenever [they] can" with the couple.
Aniston and her Wanderlust co-star Theroux have been dating since May.
They currently live together, splitting their time between New York City and Los Angeles.
Jennifer Aniston recently laughed off rumours that the pair are engaged to be married.
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