Can a woman suckle a grown young man so that he becomes her son and mahram, and will her daughter become his sister through suckling, and what is the Shar'i ruling on that?

You have erred in your dealings and seclusion with the woman, for the Prophet, peace and blessings be upon him, said: "No man should be alone with a woman unless there is a mahram with her." Seclusion with a non-mahram woman is forbidden, and if there was physical contact, the prohibition is more emphatic.

As for the suckling of an adult, the view of the majority and the four Imams is that it does not create a prohibited relationship (tahreem). They cited the Almighty's saying: "And mothers suckle their children for two full years" (Quran 2:233), and the hadith: "Suckling is only that which fills the stomach." An adult's hunger is not satisfied by suckling. Some, however, went to the extent of prohibiting marriage due to the suckling of an adult, citing the hadith of Salim, the mawla of Abu Hudhaifah.

The view of the majority is the more preponderant. So, if that woman suckled you, she does not become a mahram to you. You must repent and stay away from her.