Care worker dependent visa

Hello,

My cousin brother has received an offer to work as a Care Worker in the UK and that company has already advised their immigration lawyer to process his visa. My brother wants his family (partner and two children) also to join him. The company will arrange the visa only for my brother. In this case,

1. Can my brother apply for the visa for his family members too at the same time (or may be while his visa is in process)
2. Since the family visa applications are done separately, what details should he request from the company lawyer as the main applicant details ?
3. Any fund maintenance requirements ?
3. Link for any guidance or a document that explains the process ?

Any help would be greatly appreciated.

Thanks.