If a son or daughter gets married after you file Form I-130, Petition for Alien Relative, on their behalf, the marriage can drastically affect eligibility for permanent residence (green card).
U.S. Citizen Petitioner
When a U.S. citizen files an I-130 petition for an unmarried son or daughter under age 21, a green card will be made available relatively quickly. In this case, the relationship qualifies as an immediate relative category.
However, once the son or daughter gets married, the relationship gets classified as a family preference category. This could mean a significant wait for a green card. In many cases, it will add several years to the process.
Permanent Resident Petitioner
When a U.S. permanent resident files a Form I-130 petition for an unmarried son or daughter under age 21, it gets classified as a family preference category. There will likely be a wait for a green card.
However, once the son or daughter gets married, the relationship is no longer eligible for a green card. There is no visa category for married children of permanent residents. If an unmarried son or daughter of a permanent resident married before the permanent resident becomes a U.S. citizen, USCIS will automatically revoke any petition filed for that son or daughter.