adopted/adopted; both kids adopted, adopted/bio; one kid adopted, the other kid biological, a pair of aunt/uncle and nephew/niece
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Wave I Sibling Files
SIBCL2
PAIR TYPE-MOST DIFFERENTIATED
Codes
Label
adopted/adopted; both kids adopted, adopted/bio; one kid adopted, the other kid biological, a pair of aunt/uncle and nephew/niece
-
AA 
adopted/adopted; both kids adopted -
AB adopted/bio; one kid adopted, the other kid biological -
AU a pair of aunt/uncle and nephew/niece -
CO cousin pairs -
DZ DZ (fraternal) twins -
FO foster children (either one or both respondents are foster children) -
FS full sibling pairs -
GH not related pairs living in a group home -
HS half-sibling pairs -
IL pairs who are in-laws (i.e., living with a sister/brother's spouse or boy/girlfriend) -
MZ MZ (identical) twins -
NR not related pairs who are NOT step sibs, adopted sibs, cousins, etc. -
SP spousal (or boy/girlfriend) pairs -
SS step sibling pairs (includes blended families whose parents are not married, but are living together) -
UD twin pairs, uncertain zygosity