What if Toot isn’t the Mom but Stanley is the father? Maybe Toot couldn’t have children and when Stanley got the black barmaid pregnant, they wanted the baby but not the disgrace, so Anne took the blame. That would explain why Mom was never interested in her son but the grandparents raised him. *taking off my tin foil hat now* but stranger things have happened in many families.
That is a valid theory, for certain. But also, he favors Malcolm X quite a bit. It would not surprise me to find that Obama Sr. was tagged to cover a known indiscretion.