First, it is important to note that unlike American state law, a valid marriage under Sharī‘a has minimal requirements: oral marriages and polygamy are valid. Islamic public policy favors legitimacy rather than illegitimacy.
With that in mind, according to Sharī‘a inheritance rules, a relative inherits automatically as part of the fixed default-distribution system. Under Sharī‘a, only biological children from a valid marriage are Islamic heirs entitled to inherit from the paternal line. An illegitimate child (a child born outside of marriage) is not an heir under Sharī‘a; they take the name of their mother and inherit only from the maternal side.
However, that doesn’t mean the child would not be entitled to inherit through bequests. Sunni Islamic law permits you to leave up to 1/3 of your estate in the aggregate to non-Islamic heirs. If you want to leave something for illegitimate children, for example, you can leave up to 1/3 of your estate for them to share.
Use our ISLAMIC WILL software to prepare your own customized Islamic estate plan that is legally valid for your state, which will allow you to leave a bequest for children born outside of marriage.