No, your Nephew will not need to file a Tax Return if his only income was the SSA 1099 Survivor's Benefit.
Also, if you claim your Nephew as a Dependent, you will not need to include his SSA 1099 Survivors Benefits on your Tax Return.
Check out the TurboTax FAQ below to review the requirements you must meet in order to claim your Nephew as a Dependent:
https://ttlc.intuit.com/replies/5187060