"Become a part of the family" and "be welcomed into the family" are two synonyms for the phrase "be one the family". Both expressions suggest a sense of belonging and acceptance within a group of people who share a common bond or lifestyle. Other synonyms might include "join the family circle", "be embraced by the family", or "become a member of the family unit". Each of these phrases conveys a similar sentiment of inclusion and support, emphasizing the idea of being taken in and cared for by those around you. Whether you are joining a new family or rekindling your connections to an old one, these synonyms can help capture the warmth and intimacy of the experience.