Brothers Kyle and James Smith from the Vale of Glamorgan were both travelling in the same car which crashed in 2005.
Kyle was 16, not wearing a seatbelt, thrown from the vehicle and died.
James was 15, wearing a seatbelt and survived.
Their mother Angie Smith says she has "no doubt" that she would have lost both boys, had James not been wearing a seatbelt.
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Organisers say there will be increased security at the Urdd National Eisteddfod, which began in Bridgend today.
Any remaining heavy or thundery showers will clear eastwards this evening.
Over 70 firefighters are currently tackling the fire, which is now confirmed to be at a scrap yard.