The doctor and his wife, who...

Which are correct:

1)) An engineer and his wife who worked for us were arrested last night.

2) An engineer and his wife, who worked for us, were arrested last night.

3) The doctor and his wife who worked for us left the country.

4) The doctor and his wife, who worked for us, left the country.

In which case:

a) both people mentioned worked for us

in which case:

b) only the wife worked for us

and in which case:

c) one cannot tell

I am assuming that one can only have one wife.

Gratefully,

Navi.