Article continues below advertisementOK! can reveal Kristen Bell and Dax Shepard - long admired for puncturing the myth of Hollywood perfection - are facing whispers their famously candid marriage may be under strain, as shock rumors about threesomes and "key parties" collide with concerns from friends that the pair's public sparring has taken on a sharper edge.Actress Bell, 45, and Shepard, 51, first met at a friend's party in 2007 and married in 2013.