why lord velrmot wont kill harry potter? harry was boy who lived. maybe he miss james and lilly potter

Vildemort tried many times to kill Harry. He never had any affection for James and Lily. It would be best to explain the full story. I'll keep it as short as possible.

Probably a few days before Voldemort killed the Potters, Snape overheard the prophecy. I won't write it here, you can check elsewhere for full details. Anyway, the prophecy could have been about one of two boys. Snape thought it was just Harry. He wanted Lily's family protected, as he loved her. It failed, thanks to Peter Pettigrew.
Lily placed herself in front of Harry, sacrificing herself for her son. She gave him a special protection. As long as he has it, Voldemort can never touch him. Also, Voldemort's soul had been rendered very unstable. At the time, he had six Horcruxes. He may have planned to make the seventh with Harry's death.
So, Voldemort turned his wand on young Harry. Thanks to Lily's protection, the curse rebounded upon the caster. In that instant, Voldemort's body was destroyed. A piece of his soul latched itself onto the last living thing in the house: Harry. He became the seventh Horcrux.
As long as Harry lived, Voldemort could never truly die. But that comes in later.
Harry is the Boy Who Lived because he is the only person to ever survive the Killing Curse.
Because he is a Horcrux, he has many of Voldemort's abilities. Most notable is that Harry is a Parselmouth. Harry can also see into Voldemort's mind. Voldemort cannot possses Harry without great pain, as Harry's soul is whole and untarnished.

All of this is explained and demonstrated in the Harry Potter books.