Probably not as rare as most people think. As I've said before multiple times, 1 Cor 7 applies both ways. His body belongs to her.
Just as I pointed out men should do things to improve themselves to fix this situation so should women. She should examine herself and how she might be contributing to his denial. Specifically with respect to how pregnancy and childbearing play into this...
Has she let herself become unattractive? A good majority of women let themselves go after having kids. Are you in shape? Are you the same weight you were when you got married/first met? Are you still doing the things you did before to attract him and be attractive or have you settled into frumpy mom clothes, messy hair and no makeup? This also plays into the dynamic when men are denied. A woman when pregnant / after birth often doesn't feel attractive, and this messes with her desire. Helping her stay in shape, helping her understand you still desire her / find her attractive can help the situation.
Are you treating him like one of the children? Are you allowing the children to rule your life, or use them as an excuse to rule his, or do you place him first in your life?
Are you allowing the children to distract you from sex? Are you doing the soccer mom thing and not leaving time for your man? For young parents, are you allowing a baby who sleeps in bed / in the room to come between you?
When does he most want sex? Weeknights? Weekends? Mornings? Figure that out and rearrange kids activities to free you up / keep them quiet during those times.
Some men have a sexual hangups around the madonna/whore dichotomy and he may have a hard time feeling attracted to or wanting to do certain sexual things with the mother of his children. I'm not entirely certain how to handle this situation other than watching your interaction with him and how you project yourself to him. Do you still interact with him as his lover or have you settled into a Mom persona? Role playing might help. Or being intentional about romancing him.
Is your fertility waning? As women's fertility wanes and they head through menopause their desire for sex goes down. Usually this plays into the dynamic where a man desires sex more than them. But it goes both ways. The hormone profile of a fertile woman is sexually enticing in and of itself. As you age, that affect wanes and further erodes his desire; requiring you to up your game to stay as attractive. One thing you can do: jump him when you're ovulating, you'll be most attractive to him then. Also
avoid hormone based contraceptives as these mess with your hormone profile and his appreciation of your beauty. If there is a sisterwife, and she is younger, that fertility boost may cause him to more often become desirous of her simply because she's hormonally more enticing (i.e. it's not personal).
Now, I answered that in a limited fashion as it intersects with child bearing to stay on topic. There is a ton more that could be said but would take us off topic. If you'd like a fuller answer let me know and I'll start a new thread on that subject.
