Family terms in French distinguish between formal and everyday usage, and the words for sons, daughters, and siblings form the basic building blocks. La mère is "mother" and le père is "father," while the informal counterparts maman ("mom") and papa ("dad") are used at home and with close family. For siblings, le frère means "brother" and la sœur means "sister," as in J'ai deux frères et une sœur ("I have two brothers and one sister").
Children have their own terminology. Le fils means "son" and is pronounced so that the -ls is heard, while la fille means both "daughter" and "girl," so context is needed to determine which is intended. The plural les enfants covers both sons and daughters. Note that fille as "girl" can be confusing for English speakers, since the related English word has shifted meaning; in French, une fille is simply a young female, whether or not she is anyone's daughter.
For extended family, les grands-parents means "grandparents," with le grand-père as "grandfather" and la grand-mère as "grandmother." Informal terms of endearment include papi or papy for a grandfather and mamie or mamy for a grandmother, mirroring the shift from père/mère to papa/maman between generations. These kinship words tie together the pronouns, articles, and gender agreement patterns seen earlier — every family member's noun is either le-masculine or la-feminine, and when referring to more than one relative, les is used regardless of gender.