Nate might be brave and determined. He could be the kind of trainer who doesn't give up easily when facing tough Pokemon battles. Yancy could be more of a strategic thinker, always coming up with clever plans to outwit opponents. As for X, if it's a Pokemon, it could be very loyal once it forms a bond with Nate and Yancy.
Nate might be a curious character, always eager to discover new things about Pokemon. This trait leads him to explore different areas and meet new Pokemon. Yancy could be empathetic, able to understand the feelings of Pokemon and other trainers. If X is a Pokemon with unique abilities, it may be mischievous, often getting Nate and Yancy into unexpected situations which they then have to figure out how to get out of.
Nate could be shown as a bit impulsive at times. He jumps into situations without fully thinking them through, but his heart is always in the right place. Yancy, on the other hand, is calm and collected. She's the voice of reason in their adventures. X, if it's a special or legendary Pokemon, may have a noble and protective nature, using its powers to safeguard Nate and Yancy when they're in danger.