How can I send clients IP address with data from server to another client?[C#]

I have client 1-server-client 2 model using TCP socket. I have successfully achieved sending data from client 1 to server telling the server that "Data is for client 2" and server successfully sends data to client 2 but how can I let the client 2 know that data is from client 1? As the sender for client 2 is the server. I don't know how to process the sender information to client 2 from server. As there will be 100's of clients interacting with each other. I wanted to know a way to transfer sender information with data so that client can receive sender IP and data together.