In all the years of running this website, we've ran into a few cases as complex as the one of Toto Tamuz.
Toto is a Nigerian-born Israeli soccer player. He is a striker who has led the Israeli league in scoring and has featured for the Israeli national team. Nothing complex yet.
Toto's father was also a Nigerian soccer player. He had a contract to play in Israel, so he moved there with his family. The contract was cancelled, and the parents left the country, ditching young Toto. He was adopted by an Israeli woman, Orit Tamuz.
Orit raised Toto as her own. She raised him as a Jew, attending temple and performing kiddush, but Toto never officially converted. He clearly was not born a Jew, but he was raised a Jew, and he has lived his life as a Jew. So... does that make him a Jew?
Complex? The case might be complex, but the verdict is simple.