In the next sentence, Tacitus says, "These mysterious prophecies had pointed to Vespasian and Titus."

Virgil's Eclogues are obscure poems and can be interpreted in many different ways, The child could be the hoped-for offspring of Marc Antony and Octavia the Younger. The child could be Virgil's poetry itself. The poem could also be messianic and influenced by Jewish scriptures.

In the Life of Augustus (the title is a clue), Suetonius says the king would be Augustus: "a few months before Augustus was born a portent was generally observed at Rome, which gave warning that nature was pregnant with a king for the Roman people."

I don't recall Jesus ruling as a king over the Roman people.