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News of the relationship initially seemed to hit her estranged husband hard.
Interviewed in LA airport, the British musician said he wished she'd waited before becoming involved.
He added: "I guess you all now have the answer you have been looking for for the last seven months."
"That's what happens when two people separate, they move on and generally meet other people in their lives.
Seal went on to emphasise that the couple's four children – Heidi's eight-year-old daughter Leni, whom he formally adopted, Henry, six, Johan, five, and Lou, two – are his priority.
"I certainly don't expect Heidi to all of a sudden become a nun, but as always my main priority is the emotional well-being of my children, and to be quite honest if there is going to be someone else there in their lives, I would much rather it was a familiar face."
Later his representatives denied that that the 42-year-old was accusing Heidi of infidelity.
"Seal would like to clarify that he was not implying his wife was cheating on him while they were together," said the statement. "But rather he was pointing out that they are separated and the divorce is not final so they are legally still married."