I know what you mean parent son/daughter relationships usually feel really weird for at least the first few episodes of a show but Castle/Alexis (Fillion/Quinn) was perfect from the get go.
From the beginning I liked their differences in how they got things done. While Castle wasn't adverse to hard work, his charm and talent allowed him to skip the normal drudgery of common channels and jump the line. Beckett always had to grind and sometimes use deception to move forward. Their differences made the show great.