No, Laura Anderson and Pamela Anderson are not a niece and a nephew. As said earlier, the rumors regarding their relationship came due to their same surnames.
In the same way, many people speculated that the Andersons are distant relatives. Not only that, but some people have assumed that they were a niece and a nephew.
Meanwhile, there is no fact about it and everything can be confirmed that the news about their relationship is fake and circulated on the internet sources without any facts.
At the time of this post, both, Laura and Pamela have not said a single word about their relationship making it clear that they are not related to each other.