My child has just found out he has half-siblings (same father) in another home. He is shocked and hurt. What should I do?

Your child's shock must be met with gentleness and honesty, not with pressure to accept it quickly. First acknowledge his feelings: tell him that anger, sadness or confusion are all natural, and that he has the right to ask anything. Answer his questions honestly at a level suited to his age, without blaming anyone or speaking ill of any side. Give him time, because acceptance does not come in one conversation. The Prophet ﷺ said: “Indeed, gentleness is not found in anything except that it adorns it” (Sahih Muslim, Kitab al-Birr wa as-Silah wa al-Adab). If he remains troubled, a counsellor can help him express himself safely. See children in polygyny.