Two people can be in a unisex bathroom if the unisex bathroom is designed to accommodate more than one person or multiple people.
If it's a single use unisex bathroom then only one person of one gender can be in the bathroom unless you're related and in that case you could go into the unisex bathroom together.
Some unisex bathrooms are only single occupancy which means only one person can use it at a time.
Anyone of any gender can use unisex bathrooms as they are intended to be used by people of any gender, gendery identity or expression.
If a unisex bathroom is for more than one person at a time it will have stalls for privacy.
And in that case both male and females can be in the unisex bathroom at the same time and even other people that identify as male or female.
Sharing a bathroom of the other gender doesn't lead to sex, sexual situations, sexual harassment, or sexual assault.
A gender-neutral restroom outside the home is pretty much the same.
Some places designate them as ``Family Restrooms''.
Anyone can use them, regardless of their gender.
Bathrooms labelled as 'unisex' imply a male/female binary that excludes non-binary and gender-diverse people.
DCA recommends 'all-gender' as an inclusive term that serves the same purpose.
However, 'all-gender' bathrooms must be provided in addition to single-gender bathrooms, not instead of.