Well, I assume everyone they've recently cast is a Skrull, although I don't know if they're going for Veranke or what.
This would probably be a good place to introduce Hulkling. But would they keep the fake family origin?
If you mean his adoptive mom, well, I think that depends entirely on how they're planning on telling his origin story. If he starts out on Earth and has no idea about his origins like in the comics, it makes sense that they would give him an adoptive mother like in the source material. If they're going for something different (him being raised outside of Earth or already knowing about being a Kree/Skrull), then maybe they'd skip the adoptive angle, but I don't think that's necessary, because you'd be losing a lot of who he is if you do that.
Since his dad is Kree and looks human-ish...then I feel they would....but with the Skrull make up that we saw in Captain Marvel and Far From Home the age of who they cast as Skrull's is not as important because they are going to basically be covering their face and can make them whatever age they want.
Speaking of CM, Billy cameoed in Captain Marvel #28
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I mean, Olivia Colman is literally in the cast, so it's not like they are not allowing older actresses to be a part of this show.
Was hoping he would do a bit more, but at least they remembered him as a magic user. I just hope him being in space is not used as an excuse for him to never be a part of Earth stories going forward.