rip gladio was a hellion as a child also like his preteen-to-teen years are like......... pre-getting into athletics and he just completely acted out in all respects. hes probably been child arrested like thats how bad he was before he found a less destructive outlet (basically because he noticed his little sister was trying to copy him) so yeah

hes definitely..... way different than when she knew him as a kid but yeah he probably resents her like most students do teachers of classes theyre bad at and then also the familial connections/childhood comparisons make that worse
which is great because he and noctis are gonna start out pretty much hating each other before they start to tolerate one another over time lmao