Do any grand theft auto san andreas characters appear in gta iv?

Based solely on the evidence provided, the only verified information pertains to Grand Theft Auto: Vice City. No record or source is cited that indicates a crossover of characters from Grand Theft Auto: San Andreas into Grand Theft Auto IV. Consequently, we cannot confirm the presence of any San Andreas characters in GTA IV. If you require confirmation from official Rockstar materials or game data, further research from reliable sources would be necessary.