Nishant1

Also proportionate consolidation is IFRS only (although they have proposed to revise it to converge with GAAP).  
It does not have to be 50/50 ownership though - it might be an odd occurence for someone to have a 70% economic interest but share control (equally) with the 30% venturer.  But this would be a typical CFAI curve ball type questyion.  The requirement is joint control so in your original question, if one entity has control it cannot be proportionate consolidation.