Are the daughters of a divorced woman mahram to her other husband?

Question:
If a divorced woman marries and gives birth to daughters from the last husband, is it permissible for them to greet their mother’s former husband on the face? What is the ruling in that?

Answer:
Yes, they are mahram. If a man marries a woman and has intercourse with her—intercourse is necessary, meaning: if he had intercourse with her or she gave birth to daughters—then he divorces her and she marries and comes with daughters, the daughters are mahram to him, stepdaughters. They greet him, and he greets them. The best is for the greeting to be on the cheek: her cheek, or her forehead, or her nose, or something like that. This is the best, better than the mouth.
As for if he married her and divorced her without having intercourse with her—only the contract and no intercourse—then her daughters are strangers. They are not mahram to him, neither from the husband before him nor from the husband after him.