Ryan Phillippe's daughter gets embarrassed when people think he is her brother.

The 40-year-old actor - who has 15-year-old Ava with his former spouse Reese Witherspoon - has admitted he regularly gets mistaken for being much younger than he is.

He told Variety magazine: ''It's crazy. And still, I get carded constantly. My daughter hates it, because sometimes people have thought I'm her brother, and she's freaked out by that.''

Meanwhile, Ryan - who also has Deacon, 10, from his marriage to the 'Wild' star and two-year-old daughter Kai with former girlfriend Alexis Knapp - previously admitted he felt as though his ''greatest achievement'' was becoming a father.

He said: ''I love kids! Becoming a dad was a natural transition for me to make because my mom ran a day care centre in our house and so I grew up around a lot of kids.

''Being a father is the greatest achievement and the most important thing about me.''

And Ryan has also made plans to teach his children how to do Tae-Kwon-Do because it's the ''ideal form of self defence''.

He said: ''I've always been a big martial arts guy. I studied Tae-Kwon-Do from the age of eight and I've been teaching it to my kids.

''It's the ideal form of self defence and it keeps me fit. I'm not big on going to the gym every day. I like to mix my exercise up.''