Latinos LOVE calling people "Papi" and "Mami" as a term of endearment. It could be a relative, significant other, or friend. Mami and Papi means in English, mom and dad. However, we do NOT say it in that context. When we call someone "Papi" or "Mami" who isn't our parents, it is a substitute for "sweetie" or "babe".
We may say "Mamita" or "Papito" as well. It sounds sexier than the usual hun, love, or babycakes. Rest assure these words will make your partner melt and others feel special when you refer to them as such. Gosh, if Latinos were any sweeter we'd give people diabetes!