Find a Grave as a source should be rated very low. The information on the memorial is what some other genealogist has found or thinks he has found. If you are lucky the entry is for the people you want not some one with the same name.
There is one exception. If there is a photo of the tombstone the value of the information increases. But with all information, it should be verified. I have seen many errors on tombstones. My favorite is the first of the year error. This occurs in the first weeks of the new year. Every one has committed the error either when signing a check, or some other document.
When you give a date in the first couple weeks of the new year, the year given is likely to be last year. Example if the person died on Jan 10, 1900, the date may be recorded as Jan 10, 1899.