Ace and Nova were both riolus. But they couldn't be any more different than they already is.
Ace was born a crown prince. A special born from a Lucario father and Raichu mother. He was rash, hot blooded and cheerful to a fault. While Nova was born of normal Lucario's parents. There was nothing special about her until she discovered her priesthood legacy. She was also calm and reserved.
But the two were bound by the crimson string. It may be love at first sight, but the two had been inseparable ever since their encounter. It was only but a matter of time before they tied the knot.