I assume that your fraction of the house would not put you "over the top" on paying off the discharged amount of debt and leaving you some money left over? If it did, I'd definitely suggest rethinking your position, despite any good intentions of letting your brother have the house free and clear.

But even if the amount would be 100% peed away to your creditors who took the discharge hit, I don't think that refusing your share of the inheritance is a good idea. In fact it's almost out of the question... because at this late date, it is not yours to refuse: by law it belongs in your bankruptcy estate, even if you honestly didn't realize that until after discharge and/or after 180 days from filing.

Brotherly love is fine, but be careful not to both give him your fraction of the house's value, and possibly be liable for that same amount again yourself, and possibly face fraud/criminal charges in addition.

Not reporting it is bad enough an appearance, but at least if you play dumb, keep it in your grandparents' names and get caught, the equity is still there to be taken by the bankruptcy trustee when that happens. It's a strange enough situation that they'd probably just take the money, scold you, and be done with it.

But if you refuse the inheritance or sign away your part of the house to your brother in probate, it is not only a worse appearance and more active deception on your part, but your brother might have sold or mortgaged up the house by the time the trustee comes after it, leaving you holding the bag.

And the news gets only worse, because the most likely reasons he would want title to the house cleared up, is to do exactly one of those two things. Why else would someone want to change the status quo of living in a paid-off house as if they own the whole thing, when they actually own only a fraction?