The righteous man leads a blameless life; blessed are his children after him.
A man of good character (righteous) will do good things (lead a blameless life). That man will leave a heritage and legacy that sets his children up for blessings. Many of these blessings will come while he is still alive and active in their lives as their father.
But the blessings he brings can also continue in his children’s lives long after he is gone. Having observed his attitudes and actions, they will know how to live and will know the benefits of such a lifestyle. Of course, this verse is true about mommas, too!