twinship
xiphopagus
twinness
twinhood
twindle
gemellology
twinsomeness
nonidentical
cotwin
twinsie
nontwin
twinling
mirror-image twin
fraternal
twinlessness
twindom
twinning
anadidymus
identical
twinner
monozygotic twin
autosite
rachipagus
stuck twin syndrome
superfecundation
cephalothoracopagus
dicephalus dipus
twinsies
conjoined twin
craniopagus
twin oligohydramnios-polyhydramnios sequence
union
pairing
mating
Siamese twin
coupling
heteropagus
intertwinement
conjugation
sexual union
dualism
identical twin
monozygous twin
parabiosis
twimbos
syngeneic transplantation
secundogeniture
twincest
depairing
pygopagus