"Christina is a beautiful person, whom I have known since well before 'Idol,'" MacIntyre told E! News this month.
"She is my soul mate and the best way I know how to express my feelings for her is with a special song for this special day. 'I Wanna Be There' is about staying committed to someone through happiness, sorrow, tears and laughter. That's the relationship we have, and I'm excited to share the song at our wedding."