spouses hid very substantial history including sexual history from us. They flat out lied about things that they perceived would give them the upper hand in the relationship
Shehawk nails this.
My FWS, who had been married very young and divorced after a tumultuous 5 years, followed by 5 tumultuous years before I met her, did lie.
I let her know, up front on our first night together, for her benefit, that I had little experience, that my prior wife had sexual issues (which was not why our relationship ended). I had not had a partner in the three years since, not for lack of interested parties but because I had really loved my ex. She was shocked, she said she'd had "a lot more" (this was true), then she started lying and told me "like 70", and when I asked "why" she said "I really like sex" second lie.
I didn't care about her "number". I wanted to make sure that she was not married. I also did not want to get involved l with someone who had the same problems my ex had.
I also asked her if she was married, separated but not divorced, or currently in a committed relationship but not living with her partner. She told me she was divorced (true) and had recently ended a relationship after 2 years of on again off again episodes.
I also let her know about a problem at my workplace, and two prior workplaces, about a certain "type" of woman, that seemed to have a thing for me (these were all physically very attractive married women of a specific particular cultural background that is common in and around my profession). I had no interest in getting involved with someone who was willing to betray someone else (I had 4 instances in three years where I would meet one of these married or engaged women, who would immediately begin hitting on me, the first time I was flattered, then I eventually realized I was being viewed like a prize bull to be butchered in the end).
I let her know I had recently had to ask for someone to be restricted from working with me because in certain circumstances my work would occur at times when only two of us would be working alone late at night, and this latest married woman had been writing me inappropriate letters and pursuing me.
I let her know this for her benefit, and mine, so that if/when she heard something about it she would know what and why.
The bottom line, I let her know who she was dating, and how I handled my relationships. She lied, and did not truly reciprocate, while giving the appearance of doing so.
Honesty in the relationship is the key issue, from the beginning, to the end. Openness can come later, once trust has been established, but honesty should be up front and center.
It turned out she'd had 200+ partners, that she'd cheated in every single serious relationship, and was very troubled by sexuality but covered it with promiscuity. But what really troubled her was that I had truly loved my ex, despite the fact that we never had any contact again after our last meeting which was 3 years before I met my FWS, and I rarely mentioned her. I did have an old photo album, which I did not hide, but almost never looked at. This troubled her despite the fact that I loved her just as much as I had ever loved my ex, had children with her, and put her first above all else, year after year. She had this retroactive jealousy that she was not my first true love.
Ah, if only Disney would make a movie about our lives!