It's true that US Citizens ("USC") and Lawful Permanent Residents ("LPR" or "green card holder") can both sponsor the immigration of their children to the U.S. But, different rules apply to different situations.
The most important factors are whether:
the parent is the child's biological, adoptive, or step parent
the parent is a USC or LPR
the child is married or not
the child has turned 21 years old or not
And since everyone's family is unique, each one of these factors always leads to more questions. For example:
if the parent is the child's father - was the father legally married to the child's other parent at the time the child was born?
if the parent is the child's step-parent- was she or he married to the child's parent before the child turned 18?
if the child is also a parent - can these grandchildren immigrate to the U.S with their parent?
By looking closely at each family's situation, the possibilities become clear - and so do answers to more practical questions like - how long could the process take? what kind of evidence will be required? or, what happens if an important factor changes during the process?
Children, like all other U.S. immigrants, must also meet certain "inadmissibility" requirements. But, the rules aren't the same for every child. They can differ depending on some of the factors listed above. Again, every family's situation is unique. For more information, Contact Usfor an initial consultation.