Muhammad ibn Baschār (Rahimahullah- Died 252) said:
“I wanted to travel to seek knowledge, but my mother prevented me, so I obeyed her, and (consequently) blessings were placed in (my acquiring of) knowledge.”
(Tārikh Baghdād 2/102)
Answer:
There is no harm if your Mother uncovers her face in front of her husband’s children whom he had from another wife, and this is because they are from her Mahrams, Allaah The Most High said: (24,31) (أَوْ أَبْنَاءِ بُعُولَتِهِنّ) […Or their husband’s sons (24,31)]
[source: Al-Lajnah ad-Daa-imah [Fataawa almar-ah al muslimah–daar at-tawheed p.751]
Translated by: Abu Zainab (Muhammad Al-Hindee)