I'm thinking Grace's wife was Lauren (though I never liked her - as a character or as an actress). However, Will is returning, so it could be Kate Jones and wrap things up as the series closes. I think maybe Peyton is the cousin - Katya's daughter - and Irina is hiding the truth from Jack and Syd.
ohhhh that good never thought of that..................the one where nadia finds the pic of her mom and a baby in syds draw and jack told her that irina told him that the baby was of her nice,,,,,