In the digital age, collaborative data can be collected massively at low costs. Genealogy sites are blooming on the Internet to offer their users the chance to recover their family tree online. The collection and digitalization processes done by these users can potentially be reused in historical demography to complete the knowledge of our ancestors' past. In our study, based on records of 2,457,450 French or French-born individuals who lived in the nineteenth century, we show that it is possible to find, although some biases sometimes remain, certain results of the literature. We propose to explore the temporal characteristics contained in the family trees to study longevity. We also investigate the spatial characteristics of the data to analyze internal migrations of France.