I don’t understand how a relative pronoun can agree with its antecedent in person. Shouldn’t they only agree in gender and number?
Please see Smyth 2501:
A relative pronoun agrees with its antecedent in gender, number, and person; its case is determined by the construction of the clause in which it stands.
οὗτός ἐστιν ὁ ἀνὴρ ὅς ἦλθε this is the man who came,
αὕτη ἐστὶν ἡ γυνὴ ἢν ἐζητοῦμεν this is the woman whom we were looking for,
Thanks in advance.