I think "The pair have a son" is acceptable English. It's what I would say, rather than "has a son".
I would agree you might say "the couple have a son" not sure about a pair though.
I would agree with "the couple have a son" - any obvious reason it's not valid?
I would say "the couple has a son" because you are referring to the couple as a unit, not the individual members. (Think "The crowd chants", not "The crowd chant".) "The couple have sons" would make sense (you can think of each member of the couple having a son), but even that is a stretch.
Guess it depends on context! "The combo of female, deadpan drummer and drawling guitar-singer has been heavily imitated since, but certainly stood out when their album launched. The pair have a son together, but their relationship is now firmly artistic."
Generally agree though.
It's a difference I've noticed between American English and British English. In Am-Eng a noun that denotes a group is often treated as a singular entity, so the verb is conjugated accordingly. But Br-Eng will conjugate the verb as a plural, reflecting the multiple "parts" that make up the noun.
Ex, American English: -The council has announced... -The family has made...
Ex, British English: -The council have announced... -The family have made...
I just want to clarify my understanding. So, in this quiz, the English phrase "the couple has..." refers to American English, doesn't it?
sing.: couple plural: couples so couple is 3rd person singular. Nevertheless I think "That couple" shall be correct as well instead of "the couple"