Two of the following proverbs have similar meanings. Which ones are they?

Question

Two of the following proverbs have similar meanings. Which ones are they?

Quizplus · Accepted Answer

Proverbs are short sayings that express a traditionally held truth or piece of advice.
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Keep no more cats than can catch mice cautions against maintaining any more people or things around that can accomplish a purpose.
Still waters run deep conveys the idea that quiet and silent people have interesting and profound thoughts.
Many a true word is spoken in jest expresses that things that are joked about may in fact be true or become true.
Bad things come in threes expresses that if an unfortunate event has already occurred twice, it will happen for a third time.  
Misfortunes never come singly expresses that bad things or situations always come in groups, rather than alone.
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Bad things come in threes and Misfortunes never come singly are similar because they both refer to misfortunes occurring more than once and happening in groups.

Two of the Following Proverbs Have Similar Meanings. Which Ones Are They