The siblings, who were two of a set of triplets, were found not breathing at a house in Bridgend.
There could be a legal challenge over the new motorway, a Labour AM claims.
Traffic in Newport is expected to be heavy this weekend as part of the M4 shuts and trains are reduced.
Follow Final Score, live text, images, social media and analysis from the Premier League as Swansea face Watford.
Ospreys head coach Steve Tandy maintains there is no crisis at Ospreys after they are beaten by Benetton in Treviso.
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