I have a few important events that happened before my main character was born. He is told one of the most important ones (which explains who he's descended from) as a story when he's young, but there's many more important things that happened.
Sometimes you need to tell backstory. One trick I use is to tell it as a fascinating story in its own right, complete with rising action and a climax. For example, the second scene of a recent story of mine spends two paragraphs on backstory. I structured this passage as a sort of "mini-story," focusing on an episode in the distant past when the protagonist dragged his naked fiancé to his car, drove her to a river, and drowned her. Maybe you can find a fascinating event in the character's past and tell it in a suspenseful way while revealing the pertinent information you wanted to get across. Just remember that this technique works best after you've established the emotional connection between the reader and the character. We don't care about a random nobody's backstory, but we're always nosey when it comes to someone we care about.
Maybe do the revelations from the point of view [or dream] from the person who informed your main character of his ancestry?
Great advice. Telling has its place, and IMO this is one of them. I would just keep it short - like Michael says, a few paragraphs. Just give the necessary details to allow the reader to understand what's going on, and then drip other bits in during dialogue or narrative to enrich it.
What's the normal formula for this stuff? The MC has an item (a ring, a weapon) or a name carrying weight but never understanding why. A father's name is important, the location of a battle or devistating event, and that's foreshadowed early then revealed when the time is right.
