How to compare 2 MFCC (compare them if they where created from same speaker)
You can find the distance between the MFCC features for different speakers. The distance should be zero for the same speaker and larger with different speakers.
You can use different types of distance functions or even similarity functions used generally to compare between probability density functions.
Also, corresponding to each speaker you should generate a single matrix of MFCC coefficients which is composed of multiple coefficients for each frame. So, the output MFCC should be of dimension: (number of frames, number of coefficients).
Every speaker's MFCC dimension should be the same to compare them.