The land in Silwan was purchased in 1881 by Yemeni Jews who built their homes there until they were ethnically cleansed by Jordanians in 1929.
It still belongs to Yemeni Jews, so building by palestinians on this land is illegal.
Moreover, the Arab Muslims were so arrogant and convinced that the Jews would never come back, they did not bother to change the land registration which remained under the names of its rightful owners.