Jesus said in John 10 that “My sheep hear My voice, I call them by name, they follow Me”
They are His sheep BEFORE He calls them.
He calls them by NAME… a specific call to specific people.
They follow Him… not some follow or many follow, but everyone called follows Him.
To others Jesus said “You do not believe because you are not of My sheep” (The “of” shows possession… ie belonging to a group)
He does not say you are not My sheep because you don’t believe… Jesus said they don’t believe BECAUSE they are not His sheep.
Can the words mean anything else?
Peace to you
When you study what Christ said in context you will arrive at the proper understanding of the text.
Verses can and have been pulled out of context to support a particular view but that is not the proper way to study the bible as it will lead to misunderstanding and error.
Note in the illustration that the sheep that Jesus knows are already His own. These are ones that know Him or in human terms are people that have trusted in Him. Thus He would know their names and they would follow the one they have trusted in. Which is just what the text tells us.
Because they did not understand the illustration that Jesus had used He then went on to expland on it telling them that He was "the door" that anyone could enter through, [vs 9] "the good shepherd" that gave life to the sheep, [vs 11] those that trusted in Him.
He goes further and tells us that He has other sheep who will hear His voice and responded in trust. Not all that hear His voice will believe not because they cannot but because they will not "I told you, and you do not believe. The works that I do in My Father's name, they bear witness of Me." [vs 25]
Again He contrasts those that hear His voice and reject Him and those that hear it and believe. {vs 26-27}