Hey, advice please

so, this all started one day, me and my 18 year old brother were trying to sleep when we were visiting a tourist place with all family.

I noticed that his lap was up as an effort to try to hide his dick moving, it was obvious he was masturbating as in sometimes noises were heard and you could clearly see him moving, when he saw I was not asleep, he suddenly stopped and he looked embarrassed and was very shy talking. Since then, he does this every night

i have seen in his note adding my name with him and i presume that he imagine me when masturbating. i don't know whether he doing good or bad. so should i talk to him about this topic

I want to talk to him r, I think we could be mature, but again, he's very conservative.

What do I do? How do I talk to him? Please comment, if you have any questions about this I'll answer.

“Man can never know the loneliness a woman knows. Man lies in the woman's womb only to gather strength, he nourishes himself from this fusion, and then he rises and goes into the world, into his work, into battle, into art. He is not lonely. He is busy. The memory of the swim in amniotic fluid gives him energy, completion. Woman may be busy too, but she feels empty. Sensuality for her is not only a wave of pleasure in which she is bathed, and a charge of electric joy at contact with another. When man lies in her womb, she is fulfilled, each act of love a taking of man within her, an act of birth and rebirth, … and man bearing. Man lies in her womb and is reborn each time anew with a desire to act, to be. But for woman, the climax is not in the birth, but in the moment man rests inside of her.”

― Anaïs Nin, The Diary of Anaïs Nin, Vol. 1: 1931-1934