If you're going to make up ages, being exactly 18, and then the previous two generations of your family both had kids at exactly 20 years old, it's just too clean. You need weirder numbers, round multiples of 10 stick out too much.

Also calling it your "grandpa's" ps1, if your grandpa was 28 and your dad was 8, that wouldn't be weird now for a 28 year old to buy a console. Adults playing videogames is much less stigmatized than it once was. But if this were a real story, that would have only ever been your dad's console. 30 years ago, that would only have been seen as a child's toy.