Fiction, long-lost sisters w/ celebrity dad, Ireland/USA

This is contemporary realistic fiction book. A celebrity man dies and is on the news, and somehow his daughter in the USA finds out he has another daughter in Ireland, or vice versa. The sisters meet. The Irish sister has a cheating husband who eventually seduces the American sister. The American sister later has a summer fling with a 17-year old, the ex-boyfriend of her niece (or something like that). I read it in 2010 and am guessing it was less than 10 years old at the time. The book is light green (or at least, the version I read was). I have a picture of me reading it, but when zoomed in it is way too grainy to decipher any info at all.
Thank you!

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