If a person's Stamp 4 EU fam is revoked because the EU citizen has ceased from residing in the state, then the revocation commences from the time the minister notified the person of this. A child born to the person before the revocation, provided the person has resided in Ireland for the relevant period before the child was born, will be entitled to Irish Citizenship, and there will be no power to revoke.
If however the marriage was a sham, something the department has the burden of proving, then there was never a right to the residence card, it was fraudulently obtained, and therefore no benefit can be obtained out of the proceeds of fraud.
For people faced with this situation, the key is fighting the departments assertion, and holding them to task to demonstrate fraud. People who faced these situation, must provide sufficient information or evidence like contact, photographs and proof of cohabitation as evidence that a genuine relationship exist at a particular time in the past.
The minister cannot suggest fraud only because a relationship break down, or the couple ceased living together. He will need to demonstrate that a genuine relationship never existed, that the marriage was contracted for the sole purpose of deriving a right from community law.
Applying under Irish Citizenship child is a stupid thing and is bound to fail, as it was demonstrate the person accepting that their EU relationship was a fraud.
The key is to fight the fraudulent marriage allegation, the ability of the child to retain the citizenship, is dependent on that.
The minister does not need to revoke Irish citizenship for a born child. The citizenship cease existing by default. If they parents were residing in the state fraudulently, then they could not say they have accrued the necessary lawful residence prior to the birth of the child.
After thinking long and hard, I have come to the conclusion that brexit is a cancer. The only good brexit is a dead brexit.