Not automatically. Even in a corporate case, each joining spouse and unmarried child under 21 must be considered in the initial application and adds a separate US$15,000 fee and a separate US$1 million gift. Nothing about corporate sponsorship reduces those per-person amounts, so the company must decide explicitly whether its offer covers dependants.
Say what the offer covers before making it
An employee reading a sponsorship offer will assume the family is included unless the document says otherwise. Decide first whether the company funds dependants, funds them partially, or leaves them to the employee, and write that into the agreement with the figures spelled out. The gap between a principal-only package and a family package is measured in millions, and discovering the misunderstanding after the initial application is settled is expensive for both sides.
Add one further clause to that agreement: what happens to any commitment already made if the employee's family circumstances change. A marriage, a birth, a child reaching an age threshold, or a separation during the process can alter who is included and therefore what the arrangement costs, and an agreement written around a fixed household will not answer the question. Say plainly whether the company's commitment is a stated figure or a stated set of people, and what happens if the two stop matching.
Hypothetical example: a sponsorship agreement for a telecom network planner states a fixed contribution for a named principal and two named dependants, with any change requiring fresh approval, which is less generous than an open commitment but considerably clearer to both sides than a document that never contemplated the question.