did-you-kno:

Taylor Muhl is her own twin. She has
chimerism, which means her cells fused
with her fraternal twin’s in the womb.
Her body has 2 sets of DNA, 2 immune
systems, and 2 bloodstreams. This has
plagued her with autoimmune issues,
as her immune system is constantly
trying to fight off her twin sister’s cells. Source Source 2