The official follow up to Jaco the Galactic Patrolman and prequel to Dragon Ball has been named Dragon Ball Minus. This new bonus chapter which will reveal Goku's mother among other new material releases April 4th.
Bulma has a sibling named Tights? Vegeta not telling anyone about his younger brother Tarble makes sense to me. Tights on the other hand doesn't...maybe they'll clear that up in the manga.
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