They are likely to be travelling in a cream-coloured Elddis Autoquest Motorhome with the registration H36 PBO.
It is believed that their father Michael McKinney has visitation rights.
Their desperate mum Victoria McKinney took to facebook to reveal her daughters Grace, eight, and Kara, five have been "missing" with their dad Michael, his partner Martina and her three year old boy Woody since Thursday.
"Were visiting their father for a week but they have all disappeared, seen leaving his flat in Alyth early Thursday morning".
Police Scotland have now issued an appeal saying they want to find the children to confirm their "well-being".
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The division said in a statement: "We can confirm Grace and Kara McKinney, who were missing from Perthshire have been traced safe and well in Northern Ireland".
Police have appealed for information to help trace two young sisters reported missing in Perth and Kinross.
"Grace is described as 4'10" slim with red/auburn hair and Kara is 4'0' with red/auburn hair.
Anyone with any information which may assist officers in tracing the two girls is asked to contact Police Scotland on 101, quoting incident number 3165 11/08/17, or approach any Police Scotland officer.
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