The phrase "double lives" typically suggests someone who leads a secret or dual existence. Synonyms for this term might include "two-faced," "deceptive," or "insincere." Other possible alternatives might include "dishonest," "hypocritical," or "duplicitous." These words all describe someone who is not straightforward about who they are or what they are doing. Depending on the context, other synonyms might include "perfidious" (suggesting betrayal) or "disloyal" (implying lack of allegiance). In any case, the use of synonyms can add variety and nuance to written or spoken language, helping the writer or speaker to convey a more precise meaning.