The singer and new dad for the third time tweeted: "Mini me :)))", and on his site captioned the photograph: "Danny and I in Australia many, many moons ago."
In the picture, Peter looks just like his son by former wife Katie Price, just with a full head of curly brown hair. Nine-year-old Junior wears his hair in a close crop.
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It's crystal clear how much Peter loves being a dad – whether it's from his Instagram family pictures, his TV shows, or what he says in interviews.
The pop star, who has just welcomed baby Amelia with his fiancée Emily MacDonagh, has been sharing the experience step by step with his fans.
The Mysterious Girl singer has shown that he is a hands-on dad, tweeting a picture of himself getting decked out to carry his baby daughter.
"The best way to carry the little un :))" wrote the 41-year-old, alongside a picture of him tightening the straps of the baby carrier onto his torso.
"Thanks so much to MaByLand for this, it's so great and Ems and I use it everyday!" wrote the dad of three.
Peter and new mum Emily made their first public appearance since welcoming the birth of their first child Amelia this month at the TRIC Awards in London, the ceremony to celebrate those in the radio and television industries.
As the newly engaged pair posed for photographs, embracing each other in front of the cameras, all eyes were on the stunning Emily and her diamond engagement ring. The monster rock was clearly on show as Emily posed placing her perfectly manicured left hand against her dress.