The “Marsal” surname is properly spelt “Marçal” (c cedilla) in Catalan. This language, however, was banned in Spain in 1707 in Valencia (Eastern Spain) and in 1716 in Catalonia (Northeastern Spain), so by the time you mention your ancestors were married, particularly in official documents, Marsal will be the norm. Their birth registers may, however, be in the correct spelling, and any earlier records may be as Marçal, so try looking that up too.
Also remember that convention here rules that children inherit both parents’ surnames, with the father’s first, and the mother’s second. Thus, Esteve (in Catalan) or Esteban (in Spanish) would have the surnames Vilanova Marsal (or Marçal) in that order in birth, or rather christening records.
However, just to make things a bit more fun, wives would adopt their husbands’ surnames, with their fathers’ second. So don’t think, as I did at first when researching christening records, that I was finding that only cousins were marrying.
Good luck!