Ralston is one of Ned's two half-brothers, who first appeared (as small children) unnamed with his brother Maurice and their father and never-named mother in "Girth". They would later return in "Dim Sum, Lose Some" and "Oh Oh Oh...It's Magic". Given his age, Ralston was clearly born before Ned's mother had died and he (Ned) was abandoned by his father.
Their father showed off basic magic tricks to the twins, the same as he had once done for Ned. While Ned developed an actual magical ability, Ralston and Maurice refined their skills at stage magic. This love for magic led them to a show at the Conjurer's Castle, where their father would volunteer for a disappearing act with The Great Herrmann. Although he tells his boys "I'll be right back", he would never reappear.
Herrmann would take the two boys under his wing, and began training them. However, he was always careful to keep them a bit at a distance, fearing they wanted him to be their surrogate father figure. One day, while working on a disappearing act of their own involving two chests, the boys were visited at their home by Olive Snook and Charlotte Charles. The ladies would later bring their friend, the twins' half-brother Ned, to visit. The twins immediately embraced their sibling with love, still desperate for a family. They refer to him as 'frère piemaker', an unconditional and, for Ned, almost smothering level of acceptance.
Ralston and Maurice would invite Ned and his friends to see a show at the Conjurer's Castle, where their mentor, the Great Herrmann, would be killed in his own escape act. The twins would help investigate the murder along with the Pie Holers. Together they discovered it was another magician who murdered Herrmann, wanting to replace him as headliner, instead of the favored protégés, Ralston and his brother. Herrmann left the brothers his book of magic tricks, saying it should stay in the family, and thus acknowledging his paternal feelings for Ralston and his brother.
Olive and Chuck are both attracted to the twins to a degree, partly for the similarities to Ned, but presumably also due to the differences, since they are far more open, and tend to wear their hearts on their sleeves, even when those are rolled up for a magic trick.
The twins are not any significant part of events in the second half of the second season, and are not seen in the conclusion montage in "Kerplunk".