The couple initially broke up in May 2010 following claims that Ronan had cheated on Yvonne with backing dancer Francine Cornell.
The pair reconciled later that year but their efforts to save the marriage for the sake of their three children have failed, The Sun reports.
"Although Ronan and Yvonne couldn't patch things up, they are both determined to be there for their kids," a source said.
"They still love each other and wanted to tell their children and then their friends first, before everyone found out."
Keating's role as a judge on the Australian version of The X Factor is said to have made their battle to save the relationship even more difficult.
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