was there any reason behind of why voldemort killed harry potters parents?

He wanted to kill Harry Potter because he saw Harry as a threat to his reign. Harry's parents got in the way.

"Was there any reason behind of why voldemort killed harry potters parents?"

They were powerful, they were well liked, and they would not join him. So he saw them as a threat. He (and his minions) killed lots of people's families.

The prophecy established that parents that denied him three times, and had a son born in that month, the son would be destined to kill or be killed by Voldemort.

http://harrypotter.wikia.com/wiki/Voldemort

... about 1/5th of the way down the page

So perhaps he only killed them, because they stood between him and their son.

Because they tried to stop him from killing Harry. Harry was the one he actually wanted to kill.

He was trying to kill Harry. He killed them because they tried to stop him. Simple as that.