My grandfather, uncle and cousin are all Roberts, but they all go by middle names. Perhaps the William Fitzwilliams had a similar system?
Also, I know that in some cultures they name children based on birth order(eg Bali). So all the first born children of a certain class have the same name, all the second born children have another name and so on...
Also, I know that in some cultures they name children based on birth order(eg Bali). So all the first born children of a certain class have the same name, all the second born children have another name and so on...