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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Outbreaks of mostly light rain will arrive from the north tonight with hill fog likely.
Royal Mail says it won't deliver residents' letters because walking on a grass verge is "too dangerous" for posties.
A scuba diver from Pembrokeshire has won national recognition for her photography after coming close up and personal with a grey seal.