identical
nonidentical
twinling
twinsie
cotwin
craniopagus
twindle
Siamese twin
conjoined twin
rachipagus
intertwinement
monozygotic twin
gemellology
anadidymus
twinness
twinship
cephalothoracopagus
xiphopagus
fraternal
identical twin
monozygous twin
two of a kind
twinhood
mirror-image twin
syngeneic transplantation
twin prime pair
parabiosis
twinsies
mate
match
biosib
ischiopagus
twinning
janiceps
biosibling
similitude
dizygotic twin
pygopagus
twindom
fraternal twin
autosite
half
second cousin once removed
doppelganger
dupe
twos
our kid
ducks
deuces
monocephalus