A forbear is an ancestor or any person you are descended from, like your grandfather or your great, great, great, great grandfather.
The verb bear means to bring forth, as in to bear children. As a noun, forbear refers to a person that came before you. Your forbear can be someone you’ve known, but it can also refer to someone who came generations before you. As a verb, to forbear means to resist doing something or resist bringing it forth. You might forbear having children if you had thought your forbearers were cursed in some way.