When you said wala na ang mama mo, do you mean she is now deceased? Or if not, are your parents married? Annulled? https://www.alburovillanueva.com/annulment-nullity-marriage If she is really gone (dead), or annulled, or otherwise unmarried, then your father is not doing anything wrong, kahit landiin pa nya ang maraming babae. So walang cause para idemanda sya. But if your mother is still alive and she is still married to your father, then I believe that there is a case for concubinage. Pero sya lang ang pwedeng magsampa ng kaso, hindi ang mga anak. And under the law, hindi pwedeng idemanda ng concubinage yung mistress ng father mo without including your father sa complaint. Because of that, you would now be on a dilemma: It's either tiisin mo na lang na palaging nasa bahay nyo yung babae ng tatay mo, or tiisin mong makita ang tatay mo na nakakulong.