Your mom's or dad's first cousin would be your second cousin, there would be a blood relation and it is not recomended that there is a romantic relationship between any cousins. However some states seem to look the other way.
The relationship to your parents any cousins would be the same. If you are a female and they
are male you can call him uncle. And if you are a male and they are female you can call her
aunty. In my view no other relationships to choose.