et sic fieri cum mirarentur parentes, eam observaverunt.

[ClassicalSoul]

What does fieri do here?

Itaque praeterquam solebant mortales crescebat; et sic fieri cum mirarentur parentes, eam [Cerem nutricem] observaverunt.

The sentence makes more sense to me without it.

 

[Pacifica]

Literally "the parents marveled [at the fact] that it was happening thus (i.e. that that was happening, that is was so)".