John 8:38

With my Father

(παρα τω πατρ). Locative case of πατηρ and article used as possessive (common idiom), "by the side of my Father," picture of intimate fellowship like προς τον θεον (face to face with God) in John 1:1.From your father

(παρα του πατρος). Ablative case with παρα (from the side of) and same possessive use of του in each instance, though "the" will really answer both times. But ο πατηρ does not mean the same person. Christ's Father by contrast is not their father.