Answer
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
In this fatwa:
1- A person who sees porn stuff is not obliged to perform ghusl (ritual bath) if he did not discharge any sperm.
2- Similarly, he is not obliged to perform wudu (ablution) if his wudu is not invalidated by discharging pre-seminal fluid.
3- A person who watches porn stuff has to repent to Allah because looking at forbidden things spoils one’s heart and subjects the person to the wrath and punishment of Allah.
Answering your question, The Fatwa Center at Islamweb, states:
There is no doubt that seeing porn stuff is a kind of zina (fornication or adultery) as the Prophet (peace and blessings be upon him) said: “…Eyes commit zina and the zina of the eyes is by gazing…” (Muslim and Ahmad)
However, a person who sees those films is not obliged to perform ghusl (ritual bath) if he did not discharge any sperm.
Similarly, he is not obliged to perform wudu (ablution) if his ablution is not invalidated by discharging pre-seminal fluid. Even though seeing forbidden films is forbidden, but this, by itself, is not one of the things that necessitate ghusl or something that invalidates wudu unless this is accompanied by discharging maniyy or madhi, because if there is a discharge of maniyy, it is an obligation to perform ghusl, and if there is a discharge of madhi, it is an obligation to completely wash the penis [and then perform ablution].
However, your brother is obliged to repent to Allah because looking at forbidden things spoils one’s heart and subjects the person to the wrath and punishment of Allah.
Almighty Allah knows best.
Source: www.islamweb.net