Jay-Z's 2012 "Glory" features his daughter Blue Ivy Carter's cries and coos. At less than two days old, she became the youngest ever credited artist to feature on a Billboard chart when the song debuted on R&B/Hip-Hop Songs at #74.
Who writes a song about a name they found in a phone book? That's just one of the everyday things these guys find to sing about. Anything in their field of vision or general scope of knowledge is fair game. If you cross paths with them, so are you.