What is it that your not telling one another? There are many, many things that could cause a sexless marriage. In this case, it is because of a buried childhood secret.
If you experience Trauma of any kind as a child, teen, or adult, it can mentally and emotional scar you and hold you back from your happiness! You always have to be 100% involved, and willing to listen, understand, and talk!
You can help your partner get through this! Show them they can confide in you. Tell each other what you see in them. A great father, mother, wife, or husband. Emotionally be there!