the master document has to be with two original copies

Kill two birds with one stone, meaning succeeding in doing two things by only one action

two apartment units per floor

the slang for 'to eat dim sum' (a common Chinese cuisine); a cup of tea and 2 pieces of dim sum; minimum order; minimum purchase

two-timing (slang)

very few people

three or two gestures, which means task done quickly or in no time

three mouths two tongues, which means lack of credibility

indecisive (idiom)

describes a person who is very efficient in doing things

Three days and two nights

A few days

lit. to cover the distance of two steps with quick three steps, meaning to walk with long strides

mother and son

father and son (spoken)

both parties together; belong to both parties; both parties each have one part; two sets; split into two portions, half

both sides

a society that is advanced both materially and culturally 

husband and wife

a couple sees a ghost, which means if a couple is inside the house, and one thinks a ghost is spot, then that ghost must be his or her partner

Grandpa and grandson

a married couple; a couple

both options are plausible

Grandma and grandson

two families; both parties together; belong to both parties; both parties each have one part

lit. two coasts and four lands, including the Greater China region of Mainland China, Taiwan, Hong Kong and Macau

Cross-Strait relations, are the relations between mainland China and Taiwan

skills; ability / one's hands / method

two kinds of things combine and mixed together

moustache