If the child was the progeny of grandpa and a hooker, and he wanted to ‘adopt’ the child, what better way than to have your daughter appear in Hawaii with a new ‘grandchild’ who is then left with the grandparents to raise? A granddaughter who had a meaningless ‘convenience’ marriage (to a man that was already married ) to give the child a legal ‘father’ ???
This theory violates the premise of Occam's Razor in my opinion. Why needlessly complicate what is already complicated? (Unless there is compelling evidence to do so.)