In a binary star system, where two stars orbit around a common center of mass, it is indeed possible to see both stars under certain conditions. The visibility of the companion star depends on various factors, such as the distance between the stars, their relative sizes and brightness, and the observer's vantage point.
In some binary systems, the stars are relatively close together, and their combined light appears as a single point of light to the naked eye or even through a telescope. These systems are known as visual binaries because the individual stars can be resolved visually. Examples of visual binaries include Albireo in the constellation Cygnus and Mizar and Alcor in the handle of the Big Dipper.
However, in many cases, binary stars are too close together or too faint for their individual components to be distinguished with the naked eye. These systems are called spectroscopic binaries because their binary nature is detected through the analysis of their combined spectra. Spectroscopic binaries can be identified by the periodic Doppler shifts in their spectral lines caused by the stars' orbital motion.
In summary, whether you can see both stars in a binary system depends on various factors, including the system's distance, the stars' separation, and their relative brightness. Some binary stars can be resolved with the naked eye or a telescope, while others require more sophisticated techniques to detect their binary nature.