Meeting one's parents' expectations is always difficult for a son.
Literal
Parents [possessive-の] expectations [to-に] answering [nominalizer-こと] [topic-は], son [for-にとっては] always difficult [nominalizer-こと] is.
期待にこたえる (to meet/live up to expectations) takes に for the expectations being met. ~にとって (for/from the perspective of) marks the person affected. つねに (always) is a slightly formal synonym of いつも. こと appears twice — once to nominalize the challenge, once in the predicate.