When John Rubinstein first starred as the title character in “Pippin,” he was 25, married, the father of a newborn and making his Broadway debut. More than four decades later, he’s back in “Pippin,” this time playing Pippin’s father, and his family now numbers five children (ranging in age from 8 to 42) and two grandchildren. Though “Pippin” is a landmark show for him, Rubinstein says he never expected to be back in a production of the show, but he’s happy it’s back. There were bumps along the way as “Pippin” came to life, as there are with any new musical, and some of the clashes were between Fosse and creators Stephen Schwartz (music and lyrics) and Roger O.