(Pretty sure this is a bug)
I have been in a world countless times, and have seen Sheeps, Pigs, and Cows start showing the Breeding Hearts. I didn't feed any of them but they still showed that I did.
Just wait around your world for a while and it'll happen.
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Thank you for your report!
However, this issue is a Duplicate of MCPE-39360.
If you have additional information, please add it to that report.
Please search before reporting, as it's likely that one exists already.
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