No...synthroid does not cause black stools. This could be a sign of gastric (stomach) bleeding, certain foods, or a medication (like Pepto Bismol)... A. Black stools can be a sign of gastrointestinal bleeding (melena)....OR it can be a sign of someone taking Pepto Bismol for their loose bowel...
A person's brother or sister. Classified under: Nouns denoting people. Synonyms: sib; sibling. Hypernyms (sibling is a kind of...): relation; relative (a person related by blood or marriage) Hyponyms (each of the following is a kind of sibling): half blood (one of siblings who have only one parent in common) quad; quadruplet (one of four children born at the same time from the same pregnancy) quin; quint; quintuplet (one of five children born at the same time from the same pregnancy)
Full siblings (full brothers or full sisters; or brother and sister) have the same biological parents and are 50% related (full siblings share 50% of their genes out of those that vary among humans). Identical twins by definition are 100% related.