Wedlock Block

A couple or several couples are ready to get married, but they're not allowed to (probably because someone's parents won't allow) because someone else's nuptials (usually an older sister's) have to take place first. This can cause delightful complication if a lesser priority couple needs to Altar the Speed. Settle for Sibling is often the result of this.

Film

 * One of The Brady Bunch movies has the parents reluctant to officially approve Jan's marriage plans because Marcia is single. Marcia explains this problem to a random male stranger she meets...resulting in a Fourth Date Double Marriage with Jan and her beau.

Literature

 * Found frequently throughout the works of Jane Austen. Though it is not required, it is considered highly improper if the daughters do not marry in order of their birth - the only time it's acceptable is if the older sister slips into the category of "Old Maid" around age twenty-three. Furthermore, it's considered unusual (as in Pride and Prejudice) to have the youngest daughter (of five) "out" (accepted as grown-up and eligible for marriage) before the eldest is married.

Religion

 * The Ur Example is Jacob's story in The Bible, which play with this trope in that while Jacob wants younger daughter Rachel, Laban wants to marry off older daughter Leah off first, so tricks Jacob into marrying both of them in succession, securing seven more years of Jacob's labor for Rachel.

Theatre

 * In The Taming of the Shrew, Baptista will not give his younger daughter Bianca's hand in marriage before he finds a husband for Katherina, his shrewish older daughter.
 * In Once Upon a Mattress, a law forbids anyone in the kingdom from marrying before Prince Dauntless does.

Truth in Television

 * If you and your fiance get engaged around the same time as close mutual friends or relatives, someone will almost certainly have to wait, unless they agree to go for a double wedding option. This is not only to avoid Claire and Dan upstaging Alice and Bob, but also because of the expense the mutual friends and family would have regarding wedding gifts, bridesmaid dresses, etc.