Frank was a friend of Red's prior to Laurie and Eric's birth. On Halloween of 1957, the same night that Kitty announced her pregnancy to Laurie, Frank attended the halloween party that Kitty and Red hosted. During this time in Red's life, most likely due to influence by Frank, Red was immature and picked on kids.
We learn it's through Red's disapproval of Frank's personality of being an "ass" and "dumb" that Red came up with his catchphrase insult "dumbass."
Frank wasn't seen ever again. We learn in "Hunting" that while on a deer hunt with Red, Frank shot a deer and danced in celebration. He went to kiss the deer on the mouth but the deer was actually still alive and kicked Frank in the throat. Frank died as a result. He is portrayed by Pat Finn.