The best thing you can do is not ask about prior relationships like this.
It is information that serves no purpose but to cause problems.
The one thing you do need to know from a partner/mate is if there are STDs that are present and incurable. That is about it.
Now the information has been given honestly and you have to sit with it and wrestle with it.
The best way to look at it is everything she/he experienced prior to you made her/him the person they are now. And that person because of all of their lifetime of experiences may not be perfect as far as everybody else is concerned but fits with YOU perfectly. Like a puzzle piece.
Each experience was a notch carved here and there just as your experiences were carving notches into you and so - when you finally meet - the notches match up.
My husband was a total player before we met. I was a female version of that.
But somehow we understand each other and fit together in a way that is nothing short of miraculous.
So I am thankful he did whatever he did and experienced whatever he did that molded him in a way that he is absolutely perfect for me.
If one of those people hadn't been in his life who knows if he'd be the same. They are like forks in the road - each one taking he and I in different directions until our paths crossed.
I choose to appreciate all of those decisions in his life that brought him to me.
And yes, Softsoul, I do think I am the best he has ever had or can ever find. He's as lucky to have me as I am to have him.