Trisha Yearwood's "She's in Love with the Boy" is about a girl planning to marry one of her friends: "even if she's gotta run away, she's gonna marry that boy someday."
Tim McGraw's "Don't Take the Girl"
Jody And The Kid by Kris Kristofferson tells the story of a boy who is admired and constantly followed around by a younger girl. Flash to decades later when the now grown man and woman are walking down the same paths hand in hand, under the same nickname, "Jody and the Kid" given to them by the town elders.
"The Search Is Over" by Survivor. The singer is searching for "the one" and finally realizes that it's his lady friend who's been there for him the whole time. A Truth in Television, since writer Jim Peterik based it on a friend of his.
Pulp's single "Disco 2000" is sung from the perspective of a male version. The song lyrics start by stating the guy and the girl were born the same day, they were raised together by their moms (who even said they could've been sister and brother), etc.
The song "Todo ha cambiado" ("Everything has changed") by Chilean music group Canal Magdalena deals with a male friend who tries to change his situation, yet fails.
Flight of the Conchords' "Bus Driver's Song" is narrated by the bus driver, who keeps derailing his tour of the town to talk about Paula, a woman who used to live next door to the driver when they were little. The driver used to think they'd get married one day, but she married someone else.
"She Hasn't Always Been This Way" by Doc Walker has a guy coming to terms with a sudden crush on his best friend's little sister (also a friend of his) who is now very hot. They're not friends any more, and she won't even talk to him.
"May" by James Durbin is the story of a very tragic version of this. The two kids grow up and get married, but the title character dies in childbirth and from that point on, the protagonist can't help but see her every time he looks at his daughter.
The video for Kelly Clarkson's song "My Life Would Suck Without You" shows Kelly's dysfunctional relationship with her boyfriend starting when they both were children.
The song ''Naisho no Hanashinote Secret Story, with lyrics by supercell has the singer lamenting that her school crush, might have their eyes on someone else, and hopes they will one day realize her feelings for them.
Vocaloid Len Kagamine's "Fire Flower", in which he sings to his childhood sweetheart that his love for her is as intense as a firework.
A homosexual variant seems to occur in the music video for Joey Graceffa's "Don't Wait"; the story begins with one of the two boys saving the other from bullies. After a timeskip, a grown up version of the boy who was rescued saves a man wearing the same necklace as the boy who rescued him, implying that this man and the boy were one and the same. Afterward, they kiss.
YouTube singer Jayn has a song called "Smoke and Mirrors", which implies that the narrator and her crush were this. Then her crush fell in love with another girl. The narrator proceeds to turn into a Yandere, tries to get her crush to marry her instead, and when he refuses, she kills the other girl (who's implied to already be married to the narrator's crush).
The Lumineers' song "Flowers in Your Hair" tells a brief story of how the narrator and a girl grew up together, first as innocent kids and later as self-assured teenagers. Apparently, the girl developed feelings for him, and he tells her that he finally loves her back.
"Where Did You Go To My Lovely?" and "Last of the Breed" by Peter Sarstedt is this story Marie-Claire left her lover for money and power.