Yeah its true. As any character you cannot marry a cat. As a Cat you can get married but it would seem that is going aginst the morals of cat kind!
I have Mjoll as a wive and use her as a follower where sneaking is not required, she is awesome! Gives me money, beats the shit out of monsters with the warhammer I made her! I will have to stop using her soon as she stops leveling with you at level 40 and I am 37
I use Aella when I want to sneak and will use her between level 40 and 50, then i will be forced to use that F**kwit J'zargo for the rest as he is the only one that levels with you all the way to 81