Complex sentence: He (Peter) walks to meet the two other protagonists, his American brothers, Francis (Owen Wilson) and Jack (Jason Schwartzman), neither of whom or he have seen each other for a year, since their father's funeral.
Split into simpler sentences: He (Peter) walks to meet the two other protagonists, his American brothers, Francis (Owen Wilson) and Jack (Jason Schwartzman). None of the brothers has seen the others for a year, since their father's funeral.