Here's a quick list of vocabulary for describing family relationships. Since normally the family is taught in Basic 1, It is good to have a reference list for those learning English or Spanish
pariente: relative
parientes: relatives
familia: family
padre: father
papá: dad
madre: mother
mamá: mom, mum (British)
papas, padres: parents
hermano: brother
hermana: sister
hermanos: brothers and sisters (or just brothers)
hermanas: sisters
hijo: son
hija: daughter
hijos: children (sons and daughters or just sons)
hijas: daughters
tio: uncle
tia: aunt
tios: uncles and aunts (or just uncles)
tias: aunts
suegro: father-in-law
suegra: mother-in-law
cuñado: brother-in-law
cuñada: sister-in-law
esposo, marido: husband
esposa, mujer: wife
primo: cousin (male)
prima: cousin (female)
primo, primo hermano: first cousin (male)
primos: cousins (male and possibly female)
primas: cousins (female)
sobrino: nephew
sobrina: niece
sobrinos: nephews and possibly nieces.
sobrinas: nieces
abuelo: grandfather
abuela: grandmother
abuelos: grandparents
bisabuelo: great-grandfather
bisabuela: great-grandmother
bisabuelos: great-grandparents
tatarabuelo: great-great-grandfather
tatarabuela: great-great-grandmother
nieto: grandson
nieta: granddaughter
nietos: grandchildren (male and possibly female)
nietas: granddaughters
bisnieto: great-grandson
bisnieta: great-granddaughter
tataranieto: great-great-grandson
tataranieta: great-great-granddaughter
tío abuelo: great-uncle
tía abuela: great-aunt
padrastro: stepfather
madrastra: stepmother
hijastro: stepson
hijastra: stepdaughter
hermanastro: stepbrother
hermanastra: stepsister
Please note that in Spanish, "familia" normally refers to the immediate household of parents and children. Normally the extended family of aunts, uncles, cousins, etc. is NOT inferred at least not in Mexico. When someone not in the atomic family is at an event, he or she is also mentioned.