Bear in mind that fathers' names in marriage registers are often obtained by the minister while talking to the couple as part of the preparation. They might give the name verbally, with the minister writing down what he thinks he hears; or if it's in writing, the minister may have to interpret some rather dodgy handwriting. Either way, mistakes are very possible.
I agree it looks like Juchem, but the nearest I could find in a list of Polish forenames was Julien. You might need to look for corroboration from other sources, eg the father's death certificate, or the marriage of one of the groom's siblings - or might there be a notice or report of this wedding in a local newspaper?
Arthur