While researching my book "everycubever" (https://eckhartzpress.com/shop/everycubever/), I did a deep dive into all-star game history to see which Cub did what.
In all, 27 Cubs outfielders have played in the all-star game, but only six of them have started more than one. Frank Demaree in the 30s (twice), Bill Nicholson in the 40s (twice), Hank Sauer in the 50s (twice), Billy Williams in the 60s (twice), Andre Dawson in the 80s/90s, and Sammy Sosa in the 90s/00s. Andre started four times, and Sammy started five.