• Starlight is close in age to the Mane Six

• Starlight is close in age to the Mane Six  
• Sunburst seems to be close in age to her, but might be a bit older, especially given how he looks in the present  
• Sunset is older than Twilight, by a fair amount actually, if you take the prequel EG comic into account
   
  Aside from the age gaps/errors I really do like this idea. It also adds a whole new layer to Sunburst’s failings… trying to live up to his big sister as well, and then her vanishing without a trace years later. So there’d be even more pressure to be a “great wizard” and not knowing if Sunset is even alive, no wonder he’d pretty much forgotten about Starlight until she showed up many years later.