So far I have had five of the six of the 2legs in a party, And Boone was the default active sidekick, haven't tried Lilly yet. Which means Boone can not go into a DLC. I have brought sidekicks into both HH and OWB. I had to dismissed Boone for HH. And OWB did that for me.

Knowing this should prove usefull to those who want to use the sidekick glitch.