i see what you did there. JEHO is a strong version of HO. but JI does not have a sibling of that sort. JEJI does not exist. (and JEJÍ is a possessive, her/hers.) JI actually embodies the qualities of both HO and JEHO.
No, there no preposition in Czech there. English is irrelevant and so is German, Cantonese or Swahili, Czech does not care if any of these languages does or does not use a preposition in the ewuivalent of "hledat".