Eric Anondson said:Well, to be sure here... we know that he is Walt's father. We know that Walt's mother just died. But I don't think we can say for certain that Michael was married to the mother of Walt at the time of her death yet, can we?
From ABC.com:
"Michael (Harold Perrineau) has just gained custody of his nine-year-old son, Walt (Malcolm David Kelley), after the death of his ex-wife — they are a father and son who don't even know each other."