Parents Age Gap Makes Me Uncomfortable and Sad

Hi! I am a 17 year old girl. My parents have a 25 year age gap. My mom is 47 and my dad is 72. (Yes, you read that right.) I also have a 15 year old sister. Growing up, I never saw this as anything out of the ordinary. I mean sure, I knew my dad was older than everyone else my ages’ dads, but it never seemed significant to me. Now, however, I see it somewhat differently. To 17 year old me, it makes me uncomfortable to think about my parents getting together when my mom was only in her 20’s. I get that she was legal but it’s still kind of weird. As someone who is turning 18 in a few months, I can’t imagine even dating someone 5 years older than me, let alone 25. In fact, I am 6 months older than my boyfriend. While I realize that she was out of college and a full grown adult, I just don’t understand why he couldn’t have dated someone closer to his age, and same for her. Ever since I was much younger, I have been aware of the inevitable. Obviously, my father will be gone long before most of my friends’ fathers. In recent years, I have felt occasional anger towards both of my parents for choosing to have children knowing this would some day be the case. I don’t think it’s fair for me to live knowing that it’s a possibility my father won’t be around to walk me down the aisle or meet his grandchildren. If anything, I’m closer with him than my mother. I know my dads a good guy and had no I’ll intentions and I’m in tears as I type this but can’t help wishing my family situation looked different. Sometimes I feel very bad about myself and think that I shouldn’t be here, that maybe my sister and I are mistakes and outcasts. The thing is, no one treats me differently because of this, and my friends hardly ever mention it, at least not to my face. This is mainly an issue I feel personally. I’m not sure what I should do. I do love both my parents but I just wish I had a normal situation, with normal aged parents. Any advice or thoughts? TYIA.