Christine said that she and Kody were soulmates in the book Becoming Sister Wives. I can't find him returning the sentiment for her. But she doesn't voice any upset over him calling Meri his soulmate in the book or on the show.
It's just so weird to me that she and Janelle are selectively critical about it, especially since Kody apparently mocked Robyn for calling him her soulmate at the same time he was saying it about him and Meri. He only said it about Robyn in recent years after Christine said that he and Robyn were soulmates.
I do thinkbits weird to pass the term around. But why not express how hurtful it must have been when Kody said it about Meri or how hurtful it was when Christine said it about her and Kody.