NR == 1 { print "#" $0; }         # print record number 1 preceeded with "#"
NR > 1 {                          # for record number > 1
  l1c=l2c=0;                      # set counters
  for (i=5; i<=NF; i++) {         # for fields 5 and greater
    if ($3 == $(i)) l1c++;        # if field matches field 3 increment counter 1
    if ($4 == $(i)) l2c++;        # if field matches field 4 increment counter 2
  }
  if (l1c>1 && l2c>1) print $0;   # if counters are both > 1 print line;
}