Upvote:0
Normally you can travel separately once you have the visa. Unless there is an annotation on your visa stamp stating that you should travel together.
Nonetheless you just need to prove to the Immigration that you can finance your stay in the US.
Upvote:1
If the visa doesn't contain an annotation stating they're travelling together, they can travel separately.
As usual, they have to satisfy the CBP that they're bona fide visitors.