Mother
Madre, Mama
My mother and father are married to each other" (short phrase for 'parents')
Los padres, Papas
Not married" (adjective to describe a woman or man who has never married)
soltero, soltera
My brother's daughter (two-word phrase meaning 'niece')
mi sobrina
Grandfather"
abuelo
Father
Padre, Papa
Your female parent (formal 'your' not needed), used when speaking to a friend" (word for 'mom' or 'mother' common casual)
Mi Madre, Mi mama
The spouse of your mother" (one word)
marido, esposo
Your (singular, informal) father" (short possessive phrase)
tu padre, tu papa
grandmother
abuela
Brother
Hermano
The son of my aunt or uncle"
primo
A married couple's daughter-in-law is the wife's relation to the husband's parents — 'the husband's wife' (short phrase describing relationship to husband's parents)"
nuera
Our mother (possessive for 'our' + mother)"
nuestra madre, nuestra mama
Great-grandfather" or "great-grandmother" (one of them)
bisabuelo, bisabuela
Sister
Hermana
The daughter of my brother or sister
sobrina
"A word meaning 'only child' (one who has no siblings)"
hijo, hija
Their parents
sus padres, sus papas
Cousin (gender-neutral or unspecified gender)"
primo
Baby
Bebe
A person who is legally your parent but not biologically (one word)
padrastro, madrastra
A word meaning 'step' as in stepbrother/stepsister (prefix or adjective used before the family word)"
hermanastro, hermanastra
His sister" (short possessive + family member)
su hermana
in-laws (general term for relatives by marriage, plural)"
suegros, cunadas, cunados, nuera, yerno