sued again, same accident

What is the name of your state? PA

I was at fault in an auto accident 2.5 years ago. It was a chain reaction and all three parties sued me, and settled (signed releases), with my insurance company.

Now it appears the lead car involved is suing the other two (having settled with me already). However, the other two parties are, in turn, naming me as an additional defendant. So I have been served again. I have sent everything to my insurance company, but since they are a black hole of information, would like to know:

Is this a formality, and if not, what are the consequences?

thank you

These cross-actions are common 'gathering' tactics. Assuming you do have releases from ALL parties, then another legal claim would be 'Res Judicata' (civil equivalent of 'double jeopardy').

releases

The other 3 parties did sign releases according to my insurance agent.

Can a relative/spouse of one of the other parties still sue?