Thank you for the mass update! I got serious sweetness and heartbreak whiplash from this chapter. 😭Poor baby boy needs self-love as much as unconditional love.
And to reiterate what others pointed out:
1-Alejandro is 13 (Ch. 2 & 10) and Ibelina is 16-17 (Ch. 5). Alejandro looks younger because of the curse (Ch. 3).
2-Even before being isekai'd, the female lead wasn't that old to begin with. She looks to be a high school student, judging by her appearance and the fact she has a school bag hanging in her room.
3-Ibelina does not look at Alejandro in a romantic way and initiate ship moments. When they happen, they're either an accident—which Ibelina doesn't react romantically to—or initiated by Alejandro. Alejandro is the only one having a crush right now, which is pretty normal for his age and considering his circumstance. The one time Ibelina sees Alejandro in a more romantically-coded setting is in her dream and when he's older. Even then, she doesn't have any romantic symptoms. She's not helping him now so she can date him when he's older.
4-The whole wife-husbandry trope doesn't necessarily mean grooming or that the trope is inherently bad (look at Violet Evergreen, though note Violet's de-aged by three years in the anime). It's not for everyone and the trope can be handled poorly. It depends on the context and how things plays out. Personally, I see Ibelina as more a nurse or babysitter than surrogate parent to Alejandro—a big sister figure of sorts (I'm thinking of Nike and Livi from The World Is Still Beautiful).