Was the prodigal son reborn when he returned home? No

He was just a person that realized he had made a mistake. He repented of that mistake and the father put the ring and robe on him that the son had squandered. There is no need to be re-baptised. One is only getting wet.
When one is born again they are a son no matter what they do.
If they live a life separated from God they are still a son, but a son that is lost. You can only receive the Holy Ghost one time. There is no such thing as praying through as taught in the UPCI.