Marc Thompson said the "hardest thing is not knowing" where his twin brother Ben is.
The 34-year-old from Haverfordwest has been missing since Saturday, after he watched Wales' Six Nations game at the Millennium Stadium.
He told our Correspondent Carole Green that this would be "very out of character" for him not to contact his family.
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A bike stuntman, known as the 'Kangaroo Kid', has been injured after falling off during a live performance at the Royal Welsh Show.
Amber Davies and Kem Cetinay are the favourites to win the popular ITV2 programme, which has frequently drawn in about two million viewers.
Research by Age Cymru found that 58% of those scammed said they were too embarrassed to report the scam to an official body.