<![CDATA[The rapid development of generative artificial intelligence has expanded digital technology from an information and productivity tool into an interactive system capable of emotional responses, conversational memory, personalization, and simulated social presence. This development has accelerated the emergence of AI companions used as conversational partners, spaces for self-disclosure, sources of emotional support, and, in some cases, virtual romantic partners. This article examines sociologically the relationship between AI companion use, social loneliness, and the transformation of social relationships among digital generations. The study employs a structured integrative literature review, thematic synthesis, and triangulation of official secondary data. Peer-reviewed studies published between 2020 and 2026 were identified through academic indexing and publisher platforms, focusing on social chatbots, human-AI relationships, loneliness, emotional attachment, social support, anthropomorphism, and psychological dependence. Contextual evidence was drawn from the World Health Organization, Statistics Indonesia, and UNICEF. The synthesis indicates that AI companions can alleviate situational loneliness through perceived responsiveness, feeling heard, constant availability, non-judgmental interaction, personalization, and self-disclosure. Yet relief from loneliness is not equivalent to stronger social integration. Risks intensify when AI moves from complementing human relationships to substituting for them through intensive attachment, anthropomorphism, weak human social support, and engagement-oriented platform design. The article proposes a Relational Substitution Threshold Model (RSTM) to explain the transition from instrumental use to emotional supplementation, relational attachment, and eventual substitution or dependence. The article's novelty lies in conceptualizing AI companions as simulated relational actors capable of reshaping norms of friendship, intimacy, reciprocity, and social capital in digital society.]]>
