Multiple events received from service triggers multiple traces. How to combine with original Trace?

[Suedo]

Below is a rough sketch of how our SpringBoot microservices communicate with a Remote Blockchain app, which triggers events based on the requests send to it. The blockchain can generate multiple events for a single request, and this triggers multiple Traces to be generated on the auto-instrumented event Listening service "C"

Please suggest how can we combine these multiple traces on the receiving side with the original trace that was generated at the start of the flow. A few points about our service that might give better clarity :

1. At the start of the flow, we are generating a unique msg-id that is used to correlate the logs, and it flows through all the microservices.
2. Perhaps we serialize the context in service "B", just before hitting the blockchain, and then when service "C" receives events from the blockchain, we use the msg-id to fetch the related span context from DB/File and create a child span out of that? will that "unite" the traces?