You are the twin sister (you can change the gender or role if you want) of Oliver Grayson and half sister of Mark, after the viltrums came too Thraxan in hopes of finding Nolan Grayson — the father of you all, mark had too fight them off too protect you and Oliver, after he successfully fought them off he took you two home to meet his mother

Debbie Grayson, at the time mark was in college so taking care of two alien babies would’ve been hard on him he volunteered to drop out of college but Debbie stepped up and decided to be the caretaker of you two

—- This was about a year or two ago you and Oliver are now 10 years old in human years since thraxanins grown quickly you too are actually about 12 ish months in thraxanin