Yes, you have a claim against the title agency (not sure at this point if it will implicate your owner's policy or the agent's E&O carrier).
If the title search missed the other parties holding title, then you have a title claim and should contact your agent and underwriter ASAP to begin the claims process.
If the search showed the other parties holding title, then the agent fucked up and somehow forgot to include them in the transaction. That is a claim against the agent's E&O and you should contact the agent to initiate a claim.
As to resolution: if the others are interested in selling, then the insurance carrier (whichever is implicated) will try to purchase the interests of those parties on your behalf.