ere are just a few:

SM = stepmother

SD = stepdad or step daughter

BM = biological mother

BF = usually biological father but every now and then some use for boyfriend

SS = step son

BS = biological son

BD = biological daughter

DW = dear wife

DH = dear husband

DD = dear daughter

DS = dear son

POA = power of attorney

CS = child support

MIL = mother-in-law

FIL = father-in-law

PAS = Parental Alienation Syndrome

SO = significant other

O before ss or sd = oldest

M before ss or sd = middle

Y before ss or sd = youngest

SF = step father

CO = custody order

GBM = biomom's mother;grand BM

CP = custodial parent

NCP = non custodial parent

OP = original poster

MOTY = mother of the year

GUBM = golden uterus bio mother