this is a mistake that many people make. rather than using an attorney to set up what's best from a tax standpoint for their heirs, they just add their children (or others) to the title. this means that the portion no longer owned by them gets no step-up when they die. this can become very costly for the donee when they sell especially if there has been substantial appreciation over the time the donors were alive. your situation involves real estate but this is also true for other assets such as stocks bonds, etc.
maybe even worse, it's possible that the donee wants cash, not ownership, and can institute a partition lawsuit.
