One of the questions I am receiving is “Why am I the only rh negative person in my family?”
The answer: You are not!
You just don´t know the people in your ancestry line who are or were.
One thing about rh negative blood is that it is being passed on recessively.
It means that for 100s of years it could have been that your ancestors were all rh positive, yet carried the rh negative gene recessively.
Let´s use r as the rh negative gene and R as the rh positive gene.
If you are:
RR – You are rh positive and don´t carry the rh negative gene.
It means that all your children will have to turn out rh positive.
They can however carry the rh negative gene recessively being Rr if they receive the r from the other parent. So you can wind up having rh negative grandchildren.Rr – You are rh positive, but carry the rh negative gene recessively.
If you have an rh negative partner, they kids can turn out either negative or positive, but will for sure carry the rh negative gene recessively. If your partner is Rr like you, they can also turn out rh negative if both rs connect.
rr – You are rh negative and only rh negative.
Your children will for sure carry the rh negative gene, but it depends on the partner and chance whether or not their phenotype will be rh negative or rh positive.
For you to be rr, both parents need to carry at least one r each.
All of your family, from what you know, can be Rr with you being the one turning the recessive gene into showing up as being rh negative with both parents passing on the recessive gene to you.
Of course, someone down the line must have been rh negative on both sides of the family. But theoretically it could be that the recessive gene could have been carried for many generations without ever showing up.
And for whatever reason, you are the one who rh negative as are at least two of your ancestors.
Correction edit:
Technically speaking, it could be one ancestor responsible for you being rh negative if both of your parents are (distantly) related to each others.