When Death Watch is used, the watcher will receive a Terminated(watched) message when watched is terminated. Terminated message can't be forwarded to another actor, since that actor might not be watching the subject. Instead, if you need to forward Terminated to another actor you should send the information in your own message.

public sealed class Terminated : IAutoReceivedMessage, 
	IPossiblyHarmful, IDeadLetterSuppression, INoSerializationVerificationNeeded

[<SealedAttribute>]
type Terminated =  
    class
        interface IAutoReceivedMessage
        interface IPossiblyHarmful
        interface IDeadLetterSuppression
        interface INoSerializationVerificationNeeded
    end