Imrahil was born in Dol Amroth in 2955 of the Third Age, in the reign of his grandfather as Prince of Dol Amroth. His birth would have been cause for great celebration in the city and the family - after two daughters, and nearly ten years of child-bearing, the son of the Prince finally had an heir. The succession - which seems to have run unbroken down the male line from Imraz˘r and Mithrellas, a thousand years earlier - was once again secured.
This jubilation over Imrahil's birth is even seen in his name: it has been suggested that it literally translates as 'Heir of Imraz˘r'. While Imrahil's sisters were given historical Elvish names, he was given one that highlights his status as part of a lineage of Men.
Imrahil grew to a man in years when the shadow of war was looming. The Barad-dűr began to rise again four years before his birth, and Dol Guldur - and southern Mirkwood - again fell under the Shadow. Saruman publically broke with the White Council in 2953, and in 2954 - the year before Imrahil was born - the awakening of Mount Doom led to the final evacuation of Ithilien. All of those events were far from Dol Amroth and the Belfalas, but one struck much closer to home: Sauron's reappearance had led the Corsairs of Umbar to declare for him, and to intensify their harassment of the Gondorian coast. Dol Amroth would have stood as a bulwark against their attacks.
But, inevitably, Imrahil's thoughts would have turned inland. In 2976, the year he turned 21, his sister Finduilas travelled to the capital to be wed to Denethor, son of the Steward of Gondor. Perhaps Imrahil went with her, as a guard and a companion - not to mention to see the Tower of Guard for himself, and to make sure the much-older Denethor was kind to his sister.
And while he was there, he could well have met a certain Captain named Thorongil, who had that same Elvish feel to him as Imrahil's own family. Perhaps they struck up a friendship - but it would have been swiftly curtailed.
In 2977, Angelimir, Prince of Dol Amroth, died. His son Adrahil - Imrahil's father - succeeded him, and would certainly have summoned his heir back to the city. And so Imrahil would have left his sister - perhaps she was already visibly pregnant with the son she would give birth to next year - and returned to the coast.
Three years later, in 2980, the Corsairs of Umbar were at the height of their power. This is almost certainly how Imrahil gained his first combat experience, fighting against the ship-borne pirates. And when Thorongil passed down Anduin and struck at Umbar itself, burning their fleets and killing the Captain of the Haven, did Imrahil renew their friendship and ride with him in a foreshadowing of that other great March on an evil realm? Or did he remain at home while his father rode out, following the ancient Gondorian rule that the ruler and his heir should not both fight on the same battlefield? Whichever way the decision went, we can be sure Imrahil would have performed his duties to the best of his abilities - as he did for the rest of his long life.