I might be the last living member of birth family and not even know it the last of my kind and I just might be the only living member of birth family

I am in the exact same position and wonder the same thing. But I don't give it too much thought either. My parents will always be MY parents and I am as THEY raised me. So in retrospect I may well be the end of the line for two families blood or not and I'm almost three times your age. I've carried that thought much longer.

I am adopted , too but I think exactly the opposite, I am sure I have brothers and sisters on my biological father´s or on my biological mother´s side, some may be older , some younger, and even if I am the only one born to them as a couple I am sure they went on with their lives and had other children.

Too late to find the parents but I sure think about the hypothetical siblings often.

through 23 and me i saw i had a few second cousins but most of my family died in 1964. i wanted to replenish but was unable to.

Well, there IS one way to ensure that you are not the last member of your family.