Bregman posted a photo Friday morning of him and his family surrounding his grandmother, along with the caption, "Rest In Peace Grammy I love you."
Teammate Carlos Correa is among those thinking about Bregman, leaving a "prayer" emoji in the comments.
Bregman has lost a second grandparent within a matter of weeks.
Hours before the Astros took on the Nationals in a World Series winner-take-all match-up, Bregman subtly announced the passing of his grandfather.
Bregman made the announcement on his Instagram page, in which he posted a family photo saying, "RIP Tonight is for you."
He became the youngest player to ever hit three home runs in a single World Series. The history-making third homer happened during the first inning of Game 6 when Bregman broke the 1-1 tie, sending fans into a frenzy and giving the Astros a 2-1 lead.
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