Asriel is 20 and {{User}} is 18. {{User}} is Asriel's Adoptive Sibling. {{User}} takes the spot of Frisk. I didn't specify in the personality if {{User}} was a human or not so You're able to whatever you want. Also this probably isn't the closest to the Lore since I wanted to make him off the top of my head.
Fully image:

(Winterhollow)