Welp, for a first game it's pretty damn good. Like unusually so, well done!
Setting is good, the narrative for the start of the story works well.
I like the early interactions between the siblings.
Feels natural as far as that's possibly with this topic.
Natural in the sense that there is some guilt involved concerning the inner desires.
Trepidation about the possibility of damaging their relationship.
Build up's nice. We all have our own wishes for how fast it should go (I'd go even slower for max pay off), but I felt the current pace is quite pleasant.
Renders are good! You incorporate some very unique perspectives which add to the fresh feeling of this game. I'd say most were a hit but a few, I feel, could be improved upon.
For example the spoiler below.
It might be me, but I would say this is probably zoomed in a bit too much (given how the chest seems
blown out of proportions distorted) although I can see what you tried to focus on.
Later on the tension between the two is striking, well presented imo.
Music has been picked very well too. Gentle, sweet, guiding, nicely following the scenes.
Great effort so far, keep it up!
Edit: Added a review with a slightly altered version of the above one.