визовые дела\ грин кард.

зачеркиваю предыдущее- те у кого грин карта- могут подать на воссоединение для неженатых детей любого возраста, а вот те у кого гражданство могут вызвать только до 21 года по категории члены семьи, но родитель может вызвать любого возраста ребенка по программе семейная преференция- разница только в сроке оформления такой визы- для тех кто моложе 21 все будет быстро, после 21 года можетя занять несколько лет. читайте сайт миграционки uscis
Green Card for a Family Member of a U.S. Citizen
Is Your Family Member an "Immediate Relative?"

“Immediate relatives” of a U.S. citizen are defined as a spouse, unmarried children under the age of 21, and parents. Immediate relatives always have a visa number immediately available. To learn more, see the “Green Card for an Immediate Relative of a U.S. Citizen” page.

Family Preference Category

If the family member of the U.S. citizen is not an immediate relative, then the U.S. citizen may still be able to sponsor them via what is called a “family preference category.” Eligible relatives include:

Unmarried sons or daughters over the age of 21
Married child(ren) of any age
Brothers and sisters (if the U.S. citizen petitioner is over the age of 21)

Green Card for a Family Member of a Permanent Resident
To promote family unity, immigration law allows permanent residents of the United States (green card holders) to petition for certain eligible relatives to come and live permanently in the United States. A permanent resident may petition for his/her spouse and unmarried child(ren) of any age to immigrate to the United States. Congress has limited the number of relatives who may immigrate under these categories each year so there is generally a waiting period before an immigrant visa number becomes available. If your family relationship qualifies you as an eligible relative of a U.S. permanent resident, then you are in what is called a “family preference category.”