Generally, U.S. based sister companies are related entities because the same parent corporation owns them. Although a sister company is a business entity owned by the same parent corporation, it operates as a separate legal organization.
If a parent company has lots of sister companies, then these sister companies share common ownership and corporate parentage, yet maintain independent management, operations, and strategic goals.
A Sister company is owned by the same parent company but operates independently, while a subsidiary is majority-owned (over 80%) by the parent company, giving the parent direct control over its operations and strategic decisions.
A Foreign individual or entity can establish a sister company in the US by creating a separate legal entity that is owned by the parent company. This involves registering a new corporation or LLC in a specific US state, complying with US business regulations, obtaining necessary licenses, and meeting tax and legal requirements.