The AI has improved in its ability to create two different entities with unique attributes, though the tendency will still be to merge them. If you tell the image model a name, say, Samantha, it will use training data about Samanthas to influence the outcome. It doesn't matter if you are declaring Samantha to be this or that.
The best you can hope for is something like:
A casual photo of two different people. One is a woman with dark brown hair, aged 25, wearing a white jumpsuit and laughing. The other person is a man, aged 27, who is wearing a red jumpsuit, but he looks very upset.
You'll notice that it mixes the two characters up, because it doesn't understand the human understanding of these values. One thing I've noticed is that putting a lot of gender pronouns in a prompt increases the "gendery-ness" of a render. Just putting "she" and "her" several times increases the chances you'll get two females, even if you only describe one. The AI doesn't remember things in any coherent sense.
Yeah famous people were removed. Monroe is so iconic that you probably can't isolate the training data, the same for most presidents or elvis or people like that.
Try throwing some minor variable data into the descriptions of your character, example:
A casual photo of a genuine {23|24|25|26|27}-year old woman, she has an {aquiline|up-turned|celestial|button} nose, and is of {German|Dutch|Belgian|French|Welsh} ancestry.
The actual characteristics don't mean anything in real life, but you can get it to stop being so monotonous in the renders this way. Sometimes a simple change of age changes the template of whatever its rendering.
Another thing to try is t not rely on presets. Professional Photo is especially annoying because of how limited the "look" is. Instead, try "No Style", and hack up the presets. Try taking some of the added tags from 90s photo for example.
Also, telling it to be unique sometimes actually helps. "She has a unique beauty" and so on.
It's really annoying but possible to get it to stop doing what you describe.