Dreams often reflect our subconscious thoughts, feelings, and experiences. In your dream, several themes and elements stand out that can help in interpretation.

1. Old Coworker: The presence of your old coworker, Orion, may symbolize a connection to your past or unresolved feelings related to your work life. It could represent aspects of your personality or experiences that you associate with him.
2. Unexpected Guests: The arrival of Orion's siblings could represent feelings of being overwhelmed or invaded by outside influences in your life. It suggests that you might feel your personal space is being compromised, or you might be struggling to manage your responsibilities amidst distractions.
3. Messiness: The chaotic environment and your messy house might indicate feelings of being out of control or not being able to manage your life as you would like. This can also reflect self-judgment about your current situation—perhaps you feel unprepared for something.
4. Romantic Interest: The interaction with Orion, where he comes onto you, could symbolize a desire for closeness or intimacy. The fact that you find it enjoyable, despite initially seeing him as a "weird kid," suggests you may be open to unexpected connections or relationships in your life.
5. Ownership and Possession: Orion saying, "you're mine now," might reflect your feelings about belonging or being wanted. It could point to a desire for commitment or reassurance in your relationships.
6. Departure: His leaving with his mother can signify transitions or endings in your life. It might be a reminder that relationships and experiences are often temporary.

Overall, this dream could be pointing to your feelings about personal boundaries, the desire for connection, and how you navigate chaos in your life. Consider reflecting on your current relationships and responsibilities, and think about where you might need more personal space or clarity.