Not coincidences. It's just that as a person born of immigrant parent(s), sometimes it is played up by oneself and/or others. Myself, I was born in the Americas, but sometimes people would refer to my parents country, sometimes I would too cuz that's what some people really wanna know - "where are you ORIGINALLY from?" , but what it says on my official government issued documents is a fact.
What do Obamas' official government issued documents say? That's what really should be looked at, not what he said.
Believe it or not, lobster and crabs are crustaceans and are a part of the arthropod family, which include caterpillars, cockroaches, and spiders!