The son of the first wife marrying the daughter of the second wife

Question:

A man who had a son from his first wife married a woman, who had a daughter from her first husband. Can the son marry the daughter of this woman? 

Answer:

Yes, he can marry because there is neither blood relationship nor foster relationship between them. It is just that this man is not allowed to marry that girl and this woman is not allowed to marry that boy.

[English version of "Premier madame so garçon marié avec deuxième madame so tifille" – Al Jamiat – Vol.3 No.6]