Since a word in one language does not line up exactly with a word in another language, translation is often a matter of choosing one meaning or the other, which generally means some information is lost. It also means all translations are interpretive. Words have what is called a "semantic range," a breadth of meaning. They don't have one "literal" meaning. In this passage, is Paul saying Timothy is his legitimate child or genuine child? Is Paul talking about Timothy's legal status or character?