Hi..All four of my grandparents were born in the US. My father was born in 1931 and my mother was born in 1935. Both parents were born in Canada. My grandparents on my father's side were married in Canada in 1920. My parents have both lived in Canada all their lives. They have made periodic trips to the US all their lives. I was born in Canada in 1965.

My parents have never registered for US Citizenship. I am planning on having them apply for a passport. I understand I may have inherited US citizenship through my parents. Can anyone shed light on this? Thank you.

There is a minimum amount of time (8 yrs I think), that your parents would have had to live in the USA for you to have derivative rights.
So even if they claim their US citizenship, it won't help you. They can't even sponsor you, because they don't live in the US

You might want to know that you can acquire US citizenship or derive US citizenship. The year you were born and the years your parents lived in the States at times determines any of those benefits.
Derivation and acquisition are areas for big leaguers. You have to extra careful with whom
you are to explore your possibilites.
enrique