Having a kid is one thing - it is growing up and living to an old age. Claudius' son Britannicus did not live long thanks to Agrippina and Nero - he had an unfortunate accident. I do not imagine that Nero might look onto his half-brother with fear, envy, and reality that this brat might succeed me. The only way for the brat to live would be send him to some small island - Malta, Capri, or Elba - thus in exile he would remain until Nero dies.
The problem is what happens to the brat once Nero dies? There are two fates. Fate 1 - The populace might not want another member of that family ruling - so an accident would have to be arranged by Galba or one of his successors. Fate 2 - The senate might call him for emperor, hoping he would be like his father.