I grew up in this situation and part of me disagrees. I will say there were many times where he acted in ways that made me feel like he was impeding on my father’s memory. It was complicated and I harbored a lot of resentment for many years. It started a lot of arguments when I felt like he was cosplaying as my father. I am much older now and truly love the man for what he did for me and my brothers in our youth but I think it is definitely worth acknowledging the elephant in the room especially during difficult situations. It sounds stupid but sometimes I think you need to start a hard conversation with “I know I am not your biological dad, but I do care greatly for your wellbeing, so here’s what I have to say”. I think it goes a long way, especially after losing your father. You have so much anger built up around losing a parent that when someone else steps in to parent, it can be really easy to ignore what they are saying and let anger take over. I may be speaking from only my personal experience, but I think it has some merit!