Hmm... this is a pretty big question and one that I find so very problematic. Not in your asking, but in the idea behind me defining someone else's biracialness... Me choosing who does and doesn't count or who is and isn't “enough”.
This seems to only ever be a thing when someone wants to silence the ideas, views, opinions or voice of someone else OR excuse shitty racist behavior that allows them to project their ideas, views, opinions, or voice over someone else.
For example: Afro latinos (like myself) are often silenced within the latin community. Take a look at any social media page with a big following and you will see some real time examples of anti-blackness AS IF Afro-latinos aren't an actual thing.
Case in Point:
In her appearance on “The Breakfast Club” Dominincan singer Amara Le Negra was asked by show host Charlamane The God, “What are you?” right out the gate. He then questioned if the discrimination she faces in the industry as a dark skinned natural hair wearing Afro Latina was really an example of colorism or if it was “all in her head”. Charlamane continued to show his whole ass when he cited Cardi B (a light skinned latina) and her success as an example of how far the industry has come in accepting people who are different... thereby PROVING her point that the industry is more accepting of lighter skinned latinas and the erasure of darker skinned afro latinas.
Peep the interview for yourself:
https://thegrio.com/2018/01/22/charlamagne-breakfast-club-amara-la-negra/
Like REALLY dude? REALLY?
On the flip side of this argument... I really hate it when a large part of a specific population is upset about something and someone who may ethnically be a part of that community offers a “pass” to people and acts that are racist or offensive based on their “1/12th” ethnic heritage. This very often happens within the Native American community when they ask people to STOP wearing their culture as a costume and to change the name of the football team that means a racial slur for them.
When Native Americans say this:
Or this:
There is ALWAYS someone saying this:
I cite all this to say that at the end of the day I dont really feel it is my place to decide who counts and who doesn't. Doing so leaves a really bad taste in my mouth and allows for bigger issues likes discrimination, colorism, or outright racism to be perpetuated.
While this may not directly answer your question, I hope it offers some insight.