Wedding Letter Sam;es What Kind Of Invitation Letter/form Does My Nephew Need To Come To My Wedding In The U.S?

What kind of invitation letter/form does my nephew need to come to my wedding in the U.S? - wedding letter sam;es

I'm getting married in the U.S.. My nephew, who was from Turkey come to my wedding. You will receive a visitor's visa. What documents do you need us? Send a wedding invitation? Letter from us? Or is there a special form for this government? Thank you!