Steven, It depends where the couple want to live. Russian is useful if one wants to live in Russia.
Not easy to learn russian at 56 staying in Europe.
Exemple: do you want to live in Minsk? Ok, in this case you have to learn russian language. But it's not my case.
Well, the last year I invited an ucranian women in Tenerife. She speak only english! Well, I inscribed Marina here at spanish school foor one month lessons. Now Marina speaks spanish. Russian speakers learn languages very quickly!