Do you trust your boyfriend?
Do you believe the romantic relationship with the ex is over?
What are you insecure about?
You need to search your heart to find if there is an uneasiness with the boyfriend's continuing relationship or hurt feelings regarding the boyfriend's dad. Do you want to be the future daughter-in-law and this other woman seems to already have that role? Are you secure enough in the relationship if that is the case? Unfortunately, parents don't always have the same idea as their kids do about who would be the right mate.
Can you create a healthy, positive relationship with the boyfriend's family? Not in competition with a past love, but based on your own genuine outreach. Is there a sincere connection you could make with the family? This other woman is someone the dad has known for some time. With time, perhaps you could get to know the family better yourself and allow them to witness their child's happiness with this newer relationship.
If you are sure of your boyfriend's love and fidelity and if you truly have the foundation for a lasting relationship then be careful not to let your own insecurities undermine that.
However, if alarms are going off because you are uncertain or there are issues within your relationship, don't let the ex be a distraction. Focus on and discuss the areas of your relationship that need to be strengthened or confront any unresolved relationships now rather than on down the road.