After the divorce, he became the child's former father.

former 是形容词，意思是"以前的、前任的"，由词根 form（形式）加后缀 -er 构成，表示"从前的形式或状态"。 father 的意思是"父亲"，指有血缘或法律关系的男性家长。 former father 指"法律上不再是父亲的人"，即"前任父亲"。