he does not say souls always travel together.he says that souls which have unfinished jobs with each other travel together ..as unless you are freed of karmic bondage..you can never progress further...And lessons are repeated till we learn how to free ourselves of that..
Oh ok...my interpretation was wrong then...
But I do clearly remember that he says that every life you learn to attain higher spirituality.
Okay so one continues to be born till all the lessons are learnt.