1998 GMC Suburban "causes front end vibration 2011" Questions

...front end aligned and wheels balanced. Was worse before that but it is still occasionally occurring. Also, and this just started the in the last 2 days is a vibration through the brake petal when ...

...front end. Started driving again with no issues. I do feel a slight quiver at random and try isolate from where it might be coming from with no results. I have had the tires rotated and preventive ...