If my dad died recently and left everything jointly to my brother and I but my brother filed bankruptcy before my dad's death, can my half of the estate be at risk?

Inheritances are usually considered separate property. You and your brother are not a couple so the possibility of your portion of the estate being touched is minimal but to make it even less likely, you may wish to immediatelyt begin separating assets so your portion of the estate is not touched or that your portion right along with your brother's portion are not frozen while the court and bankruptcy trustee sort out what belongs to whom and what is ordered to be sold or used as assets to pay or settle with creditors.