The Collaborative International Dictionary of English v.0.48:

Yokefellow \Yoke"fel`low\, n. [Yoke + fellow.]
   An associate or companion in, or as in; a mate; a fellow;
   especially, a partner in marriage. --Phil. iv. 3.
   [1913 Webster]

         The two languages [English and French] became
         yokefellows in a still more intimate manner. --Earle.
   [1913 Webster]

         Those who have most distinguished themselves by railing
         at the sex, very often choose one of the most worthless
         for a companion and yokefellow.          --Addison.
   [1913 Webster]

Easton's 1897 Bible Dictionary:

Yoke-fellow
   (Phil. 4:3), one of the apostle's fellow-labourers. Some have
   conjectured that Epaphroditus is meant. Wyckliffe renders the
   phrase "the german felowe", i.e., "thee, germane [=genuine]
   comrade."