Single word to describe something that is "meant to be"

Fated seems pretty appropriate here. But also destined, preordained, and not one word but 'in the stars seems pretty apropos given the context.

EDIT - added after comment below Leon Conrad

It sounds like you mean that it was appropriate, suitable, felicitous, proper, apt, or, as I used above, apropos.

Kismet sums it all up.

Destiny; fate:

You want poetic, you'll get poetic.

Written in the stars: it was destined to happen. The belief that our fate is written in the stars is ancient (horoscopes are a modern use of that belief), and certainly made famous by Shakespear's use in Romeo and Juliet

From forth the fatal loins of these two foes
A pair of star-crossed lovers take their life,
Whose misadventured piteous overthrows
Doth with their death bury their parents’ strife...

Also, preordained: happening inevitably. Connotes a higher power meant for it to be.

all the days ordained for me were written in your book before one of them came to be. - Psalm 139

As the Fates would have it.

Another possibility would be inevitable:

adj. Impossible to avoid or prevent.

While it does not carry the connotation of fate or any indication of poetry, it is the word I'd use for something that was bound to happen.