This refers to the owner of the house with the narrow door in the previous verses. This is a metaphor for God as the ruler of the kingdom. (See: [[rc://en/ta/man/jit/figs-metaphor]])
Jesus was talking to a crowd. The form of "you" is plural. He is addressing them as if they will not enter through the narrow door into the kingdom. (See: [[rc://en/ta/man/jit/figs-you]])