Headcanon
Elim Garak is Enabran Tain’s youngest and favourite child. He had five or six other children with his wife, but none of them showed the promise in the ‘family business’ that the late-in-life mistake with the housekeeper did.
And he absolutely should have killed Mila before Elim was born. Not because he’s Enabran Tain, head of the Obsidian Order, but because it was disrespectful to his wife and children not to. That’s just Cardassian society, and any powerful man would do the same.
But he didn’t because he had a sentimental attachment to Mila. He felt a great deal of guilt about not killing her when he should have (it was detrimental to Cardassia because if the scandal had got out it might have shaken the very foundations of power and put Cardassia at risk).
He saw the spark of sentimentality in Elim and did his best to extinguish it. As well as the sentiment he himself felt for his son.
