Stan is Sandy's older twin brother, being born at least just a minute before her. Like his fraternal sibling, Stan has an interest in sports too, but is more interested and skilled in the more extreme sports like skateboarding and snowboarding. Stan is often seen with his favorite musical instrument, the maracas, and will often shake them around whenever he gets excited. Stan's most notable trait, however, is that he behaves the exact same way that Pokemon Trainer Brock does... He attempts to hit on other females every chance he gets! This often annoys the other male Ham-Hams, and the female ones find Stan a bit awkward when he flips his love switch on, but because they're too kind to want to hurt anyone's feelings, they try their best to be kind to Stan anyway. This does not include Sandy, however. She often gets angry and embarrassed when his older twin brother attempts to charm the other females. I'm sure you would feel the same way as Sandy if you had a sibling who tries to flirt usually at the wrong times.

 (For Stan's voice, I will allow his to either sound similar or identical to his previous voice provided by Mike Coleman. Here are some clips of Stan from other Hamtaro Episodes for voice reference!) 

https://drive.google.com/file/d/110-qYtfHedLwFs0BxLdTDU4TwYSOcA2M/view?usp=sharing