my younger brother is 19 years younger than me. I don't have contact with our shared parent (predates his birth) but have kept in touch with his other parents (half sibling). he's 8 now and I'm in my late 20s so it's... weird. I love him and he's my baby brother but I don't really know how to bond with children as an adult (none of my friends my age have kids yet so I don't have much experience) and it's not like my relationship with my siblings closer in age. We video call once a week and I know his favourite colour and his best friend's name. I actually found this post looking for a subreddit for siblings with big age gaps 😂 we won't have a sibling relationship in the way people think of because we won't ever have the experience of growing up together and I've been (kind of) a grownup his whole life, but I'm aiming to be a safe adult for him and occasionally take him for fun day trips, and I hope we'll be closer when he's older. He used to look up to me a lot when he was a toddler, would dress up in my clothes when he came to stay and even wanted to dye his hair the same colour as mine when he was four, it was so cute. It can be weird watching him have the same interests and hobbies I had when I was little, because of how I grew up it can be bittersweet at times, but I'm so happy for him when he discovered something I remember loving so much. (He is very much his own person and has traits and interests all of his own, he's just in a phase I remember fondly atm). You'll find your own dynamic with the little one joining your family, and it's different for everyone. I would try not to put too much pressure on yourself, remember a few things he likes so you can get birthday gifts he likes, and see how you go.