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The former couple seemed close in recent years following its bitter break-up and custody battle, and Richards even took in the actor's twin sons when their mother, Brooke Mueller, was admitted to rehab last year.
Sheen and his ex also teamed up when Richards confessed the four year olds had become too much for her to handle and they needed psychiatric help for a series of behavioral issues.
But the former couple fell out at the end of last year after she allegedly pulled the plug on plans for him to join her and their daughters, Sam and Lola, over the holidays, and Sheen started attacking the actress on Twitter.
In one tweet sent 10 days before Christmas, he posted a picture of a baseball bat given to the couple as a wedding souvenir chopped into pieces, alongside the caption, "The lie is over. I'm done being treated like a relative with a one-way ticket."
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Richards responded by asking her ex to "keep it classy dude," adding, "Our kids don't need to be privy to this, U are welcome 2 spend xmas w/ us Hope u still come. U were & are welcome 2 see them... Please 4 our kids stop this."
But now it seems Sheen is keen to start 2014 as he ended 2013 -- by blasting his ex on Twitter.
In a tweet posted on Tuesday, he writes, "Hey denise I own the farm. yet you are only pig in the pen to sling mud bile & sh--- every inch your evil cloven hoofs trample. c #Oink."
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Meanwhile, rumors persist that Sheen is hoping to evict Richards from a property he owns close to his own home in Hollywood.
- Jan. 19, 2018 See all the stars at this year's Sundance Film Festival