In indirect speech, the direct sentence "He said to her, 'I am your uncle'" becomes "He told her that he was her uncle." The direct speech is converted into indirect by changing the present tense to past tense and adjusting the pronouns.
The sentence "He said to her, 'I am your uncle'" when changed to indirect speech becomes "He told her that he was her uncle." When converting from direct to indirect speech, it's important to make changes in verb tense, pronouns, and sometimes time indicators. Since the original statement is in the present tense ('am'), in indirect speech, it changes to the past tense ('was'). Additionally, the personal pronouns also change according to the context in the original sentence.
In indirect speech, the statement "I am your uncle" would be reported as follows: He said to her that he was her uncle. When changing speech from direct to indirect, we need to shift the pronouns, verb tenses, and adverbials of time and place. In this case, the pronoun "I" changes to "he" and the present tense verb "am" changes to the past tense verb "was".
The question probably maybe:
He said to her," I am your uncle"
change into indirect speech​