Twins Knox and Vivienne Jolie-Pitt are just like their parents Brad Pitt and Angelina Jolie, with Knox taking after his dad's ''calming, relaxed personality'', while Vivienne has Angelina's ''stunning'' looks.
The 71-year-old actor - who only recently reconciled with daughter Angelina after a seven-year feud - says Vivienne has her mother's famous good looks, while Knox is as laid back as his father.
Jon told Fox News: "One takes after Angie and one after Brad, they are really amazing. The boy is very quiet, he has this calming, relaxed personality that Brad has. And the girl, well, she's just stunning like Angelina. Just beautiful."
The Oscar-winning actor joked he is responsible for his amazing 22-month-old grandchildren.
He credits it to his "good genes", but added: "Brad and Angelina are incredibly good parents."
Jon got to spend time with his six grandkids - the twins, Maddox, eight, Pax, six, Zahara, five, and Shiloh, three - during a trip to
Venice in February, where they stayed at the Suite of the Gods, a luxurious hotel that sits next to a winery and the Aegean Sea.
Angelina was in Italy at the time to shoot her latest movie 'The Tourist' with Johnny Depp.