^in which case, you are highly motivated & can immobilze everybody with court cases.
Keep track of all accounts & properties.
IF your dad dies (knock on wood, scenario lang usapan dito) -- agad agad inform banks of his death, ma freeze yang accounts until an Extrajudicial Settlement is presented. Likewise, inform the involved Registry of Deeds so ma annotate agad TCTs/CCTs -- may fees yan ha.
Be sure your mom cooperates with you. (why not naman?)
Unfortunately, bastards have the right to inherit. So, may pakinabang.
You can demand DNA testing, however.
Careful, do not let your father see your "high motivation".