Some are, many are not. It all depends on the individual. Some bi people are more romantically attracted to men and more physically attracted to women. For others it’s the opposite. Many bi people have very fixed patterns of attraction, while for others, the balance between heterosexual and homosexual attraction is fluid and changes over the years. One need not be equally attracted to both sexes to be bisexual; they simply need to be attracted to people regardless of gender or sex.