Several brehs have already said it. She hasn't lost her sex drive....she's lost her attraction to him.
This is the type of situation where GMB applies because this dude is already married, already two kids in and now his wife decides she doesn't want to have sex. Now of course we know this didn't come out of nowhere and the article already says how she had been making excuses to not have sex for awhile before. She just finally got honest about it. So, dude has been getting side-stepped for some time now.
At least she was considerate enough to let him know she's good with him having another chick. In that case, maybe they can stay married since he can have his wife for mother/financial reasons and his other chick for romantic reasons.
Personally, I think I would file for divorce since I think she's being pretty selfish in terms of just deciding that she's not going to have sex with her husband. What if he decided that he didn't want to pay his portion of bills? What if he just decided that he didn't want to help around the house?
Trick spot for dude.
Peace