No you do not have to tell her or anyone the circumstances of your birth.
Even if she were to conceive a child with your son, it would still be your private information and entirely up to you whether or not you wanted to share it.
So, she is informing your son on what he should 'know'...what does your son say? Has he asked? This would perk up my radar for controlling or manipulative behavior on her part. If she makes the issue into a deal breaker for the relationship with your son, I'd say hold the door open for her and good riddance.
Agree with TeachMySelfBalance, that information is private stuff about you, and no-one else has a "right" to know. Also think the Will idea - or a letter to be read after you're gone - is a good idea, if your DS himself expresses any curiosity.
I don't believe he has any rights that supercede yours. If you don't want to know, then that's up to you. And it's ABSOLUTELY nothing to do with his GF - she's being unnecessarily nosey.
Agree with the Will or posthumous letter for your DS, if you feel that you want to - but as to the rest, she can stick it.
While she may be asking for genetic tendencies purposes, should she choose to procreate with your DS, it's not necessarily that relevant - any recessive traits that come out on the male side should have shown up in your DS, with the exception of Huntington's chorea but that can be tested for if she's that paranoid.
Lots of people have DC without knowing their birth parents' medical history - including you - there is no enormous need to know your birth grandparents history.
If it's any consolation - a friend of mine wanted to know why her mum wasn't in contact with her mum's dad. Her mum said he was a horrible man and she had cut contact years before. But my friend, a stroppy teenager, pushed and pushed to regain contact - and discovered that her grandfather was indeed a horrible man that she came to regret finding.
It's not all hearts and flowers where birth parents are concerned - and (unless you already know who they are) there are no guarantees that you would even find a birth father.
Unless you want to find them its nothing to do with anyone. Does your dh know why you don't want to look for them? Also I didn't think granchildren could search for biological GP's unless the parent had passed away. I would tell them no due to not wanting to hurt your mother.
I can see if she wants to know from a "medical history" standpoint (if she and your DS are going to have children.) But at the end of the day it's your business and if you say no she needs to respect that.
I'd be looking for a bit more "status" than "girlfriend" before I released any information at all, and still maintain that OP's right to privacy is waaaaay more important than some random girlfriend's wishes.
Is there a "mixed race" issue here? Are there problems with rape/slavery?
I don't think they have any rights to know your birth parents if you don't want them to.
DH is adopted and has no interest in finding out about his birth parents and although I would love to know about them, I have to respect HIS decision. DS is 9 and has always known that DH is adopted and he is curious about it all but I wouldn't say he has any right to know either. And if in the future he has any girlfriend who wants to know he will be told that they both need to respect DH's decision. It is HIS life and HIS history.
Your background, your business imo. Presumably you and your DCs learnt about your family heritage already, albeit your adopted one. If that's been good enough for you so far why should you dig into your biological family just to satisfy the curiousity of someone who may or may not be part of your family in the future and risk upsetting those most important to you like your mother?
Tell your DS's GF to do one. I can't believe she had the nerve to ask for such sensitive information.
Many people who aren't adopted don't know about their heritage/background. My mother cut contact with all of her family and all of my Dad's family when I was very small, therefore I know next to nothing about any of them. My husband's family are not close, and although he had a relationship with his paternal grandparents, he knows very little about his mum's side of the family. The result is that our 20 year old and 17 year old children know very little of their heritage, just a little about my parents (what my mother chooses to divulge) and a little about their Dad's paternal family.
I think your children, and most especially your children's partners, should respect your wishes, and be content to know that they are part of a loving and close family.