The "B" in LGBTQIA+, in the narrow sense Bisexual / Biromantic means being attracted to both men and women, but many Bisexual people are actually attracted to more or all genders than that. In that case Bisexual becomes a synonym for more precise terms like pansexual, polysexual or omnisexual with some people simply preferring the term Bisexual or liking the colours of the Bi flag better.
Someone who is Bisexual does not need to like men and women equally, nor are they any less Bisexual if they only ever have had relationships with one gender. It's about attraction and what they feel, not how they act upon those feelings.
Because of the fluidity of the term and its overlap with Pansexual, it can be hard to figure out if a character is Bi or Pan (it can be hard to figure out for yourself) so for our examples we have based ourselves on the stated opinions of their creators or what they ahve said in canon. In the real world you should of course just go with what the person themselves says.