So I've had this linger in my mind for the past 5 years or so, wanted to see if anyone knows the answer

Both of my parents have dark brown hair, dark brown eyes and I have blonde hair, blue eyes, which i guess isn't that uncommon to happen but when my sister was born 7 years after I was, she also had blonde hair, blue/green eyes

Is it rare for both my sister and I to have blonde hair, blue/green eyes but our parents have dark brown hair/eyes? Or is this normal?

Both your parents carry the genes for those colours and, so, can be expressed in you and your sister. They are called recessive traits.  Dominant traits, like brown eyes, only need one parent.