Just a few minutes ago, Astra ordered Eliza to put one Mage from the Obsidian Order on Vaan to ensure his safety. What was the Obsidian Order? It was a group of elite mages that served the Head of the Vesta Family and answered to her and her alone.
Even amongst the 7 Star Mages, they are considered the elites, the strongest, and Astra had ordered one of such beings to ensure her son's safety.
No, keeping her aside, just considering Orion's nature, the man, who himself protected his son ever since he was born, it wasn't hard to guess how overprotective of parents Vaan had.
Would the mother and father not know where their son currently was?
Would they allow their son to meet a reckless, arrogant, and prideful Magic Beast, who also happens to hate him, without anyone guarding him?