When you're learning a new language, a cognate is an easy word to remember because it looks and means the same thing as a word you already know. For example, gratitude in English means the same as gratitud in Spanish.
Just as words that are cognates have a shared origin — like gratitude and gratitud both coming from the Latin word gratitudo, meaning "thankfulness" — people can be cognates based on their shared blood. For example, you and your sister are cognates of your parents. You probably even look alike, just like word cognates. The adjective form of cognate can describe blood relations or anyone whose ancestors spoke the same language.