One should remember that there is a big difference between Ishta Devata and Kuldevta in Hinduism. A person or his family may have a deity as per their inclination, convenience, and change in region etc. This is a personal deity not tutelary deity. Kul Devata or Kula Devata is the god associated with the entire community. Kula or Kulam means family or race or descent.
Tutelary deity cannot be changed for it has descended from the 'kul purush' (the first ancestor) of a kinship, who had surrendered his life and the lives of his posterity to a particular deity. The tutelary deity is of the particular kinsmen. It is associated with entire community. The first ancestors could have achieved success, peace and prosperity after worshipping the Kuladevata. The deity might have also appeared before the kul purush.
Some of the popular Kul Devatas are Mangesh, Maha Deva, Mahalakshmi, Mahalasa, Shanta Durga, Nagesh and Saptakoteshwar.