It's still amazing to me that I'm a grandfather [of four] but I love it and I've settled into it. I really enjoy being around the kids. The older girls are starting to understand what I do now for a living and starting to see me in my movies, which means they have a different view of me now they know I act. When they understood that I was Mike Wazowski in Monsters Inc, I had to talk like him for six months. It drove me crazy. Then they saw The Princess Bride, and I had to be Miracle Max for six months.

My grandparents invented joylessness. They were not fun. I've already had more fun with my grandchildren than my grandparents ever had with me. But they were really interesting people. She was Russian, he was from Vienna [Susie Gabler and Julius Gabler] and when they didn't want us to know what they were talking about, they spoke Yiddish, so we were always left out. Me and my brothers, Joel and Richard, would be sitting there and they'd say: "You know who I saw today? Blah blah blah …" and you'd go, "Oh, I guess they didn't want me to hear that."

I always think of them as old. They always seemed old. Even in their 60s they looked like they were in their 80s.They were very old school. They were wonderful people, it was just a different time. There was an old world kind of hierarchy in the family and they were the matriarch and patriarch. They lived just a few blocks from our house and, every time you'd go there, you felt like you were going some place special. It was like going to see the wise men. You actually did feel like you were going to glean some real wisdom from them. I remember them with great respect and affection.

You have to really respect what your kids are doing with their kids and how they're raising them. You can't push your way into areas where you shouldn't be saying anything. You have to always remember they're not your own kids. Play with them, love them, spoil them to death – then hand them back.

When my daughter Jenny was pregnant with our first grandchild, Ella (now 10), it was very profound for me because Jenny is my firstborn daughter. One night I wrote down all the things I was waiting to do with my little granddaughter and it became a book, I Already Know I Love You. It was one of those really lovely things in life.

My dad, Jack, had a great sense of humour and had a strong impact on me and my humour. He prompted us to watch great comedians on television. The 50s were a particularly great decade for television comics in the US. Dad had a music store and he'd often bring home comedy albums that I would listen to. I started listening to Bob Newhart and Bill Cosby, and developing taste. They really influenced my style of comedy.

My mum, Helen, was hilarious. She had a tremendous sense of humour and was a great singer and tap dancer. For many years she was the voice of Minnie Mouse in the Macy's Thanksgiving Day Parade. She would be in the float as it came along singing whatever the Minnie Mouse song of the day was. She was a really big spirit in my life.

I didn't rebel as a child. I missed that angry teenager thing. I had a really great childhood. I always loved to get up and perform. I was the youngest of three and the only thing I was moody about was that one brother is 6ft 2in and the other one is 5ft 10in. What happened to me?

I think my wife [Janice Goldfinger] and I were good parents because we didn't want to be our kids' friends. We knew we had to be their parents. A lot of parents nowadays try to be friends with their kids, and I don't think that works. Ultimately you will be friends as they get older, but when they are growing up you really have to know who you are and who they are. Also we listened to them and we were patient; we just always maintained the right amount of authority. I think we laughed a lot and we let them express themselves. We just really loved being parents.

Families need to connect and need to be together. I think grandparents have a responsibility towards their kids and kids have a responsibility towards their parents to keep the family tree together. My family is the most important thing in my life. When we're all together you just stop worrying about things you shouldn't worry about and you go, "Wow, look what we did!"

Being a family man has affected my career choices. You can't live your life for your kids or grandkids but sometimes I have thought, will they be able to watch this with me? Maybe not today but when they're 15? When my daughters were growing up, I remember thinking I needed to be careful about certain scenes and what I said and how it would reflect on them. I think you have to somehow factor that into your work but not let it rule what you do.

Kids need a happy household. They need to be loved and supported in their dreams. And I don't think you can make your kids' dreams your own. They need you to support them in their dreams. You can't make them do things they may not want to do. My girls turned out great. And the way that my parents raised me and my brothers was different but it also worked. I think it's like a relay race. You run and you hand over the baton and your kids pick it up. They take the stuff they want, throw the rest away and keep running. That's what life is about.

• Parental Guidance is released on DVD on 27 May by 20th Century Fox