Here the way I see it. Hope this makes sense.
1) You're basing this off of the Leadership feat.
2) The followers gained from the leadership feat you are the leader of and should be able to influence.
3) The other PCs you are not nessisariraly the leader off. They are usually your equals.
The followers came to you because of something you did (out of game it was gain the leadership feat, in game it could be anything). The other PCs have been with you longer, but you're not their leader in the same way as these other people unless you filled some of your NPC slots or cohort slot with the PCs.
Another seperate reason I had was to keep your followers alive. In my group when someone takes the Leadership feat they go into more then basic detail on their followers. The other PCs can take care of themselves, I think these feats should help out your followers since they will be in over their head.