Whoever quitclaimed the property can only transfer any ownership rights he/she holds.
For instance, I could quit claim the Golden Gate Bridge. It'd be perfectly legal. Problem is: I don't own it, so while I'd be "quitting my claim," I have no ownership rights, so none would be transferred.
Perhaps more relevant, if I owned a property along with someone else, I could quit claim my ownership rights to someone else. However, my action would in no way affect the ownership rights of any of the other owners of the property.
The questions your lawyer is likely to ask are: Who quit claimed the property, and when? Again, this is not legal advice. However, if your spouse's dad had written a will giving the land to your spouse, but his dad quit claimed the property to someone else before he died, then he transferred ownership. So there was really no land for your spouse to inherit. On the other hand, if his dad willed the land to his children and their spouses (let's say two sons and their two wives), then his dad died, then the land would go to all four individuals. The other son or the wife could quit claim their interest to whomever they wanted. But it wouldn't affect your interest.
Again, that's not legal advice, just a hypothetical example. So: See a lawyer. Be prepared for the questions I mentioned above.
A quitclaim is normally used to clear up any clouds on the title. If they signed away their own potential rights to the property then that should be fine. It is a little hard to answer thisquestion more fully without having a little more background on the situation. Feel free to email us at our website and I will try my best to help in any way I can.