It’s up to them what pace they want to move at, although if it’s left too long it will be harder. There may be issues they have with each other surfacing. Parental loss changes the relationship of the siblings an it can take a long time for the status quo to return. They may not know it or want to except it but clearing the house together is the best thing to do.
Three years is a long time and it all opens a big can of worms.