Your Twin Being With Someone Else
Lean into this (as you may be projecting these beliefs onto your twin):
Does this pattern of thinking remind you of any time someone asserted ownership of someone else?
ie. this could be how your parents or family view marriage. when someone belongs to you there is ownership and this may create unhealthy expectations.
What to do with it now?
Acknowledge it, release any ownership over that belief and establish your own beliefs about unconditional love. Being aware of where this pattern came from will help you to establish that you most likely took on someone else's version of the truth.
You were and are now worthy of the most beautiful love, as you are in this moment.
What if your twin leaves the karmic situation? Would you be ok with them wanting to be single, independent and want to find themselves as that is what they have deemed will make them happy? If not, there may be some extra work around love without condition for you. It's a hard concept to know that they are the other half of your soul and are entitled to live life how they choose. But that's not your soul speaking, that's the preconceived notion of how love is "supposed' to be. There may be some work around needing your twin to make you happy or fulfill your life in some way. It is not their job to do that, and they will fail miserably because they aren't you.