Mark McGrath, frontman of '90s rock staple Sugar Ray, is expecting twins with his fiancée in May.

"I love them already, but I need them to come out so I can really shower them with love," the singer tells PEOPLE. "I can't wait to meet them."

McGrath, 42, and Carin Kingsland, 37, got engaged on New Year's Eve after 16 years of on-and-off dating. Kingsland underwent in vitro fertilization, and now the couple is expecting a baby boy and girl.