There are way too many key factors.

1) Scorpius says living without Albus is heart-breaking

2) Both have common pet names for each other (which is adorable)

3) Their relationship is so deep that just the thought of not communicating with each other is heart-breaking

4) Scorpius could care less about restoring Rose to the timeline, and only does so for Albus.

5) Snape even points out that Scorpius would rather restore all the timelines if it means getting Albus back

6) They even kind of flirt with each other at the end of The Cursed Child

Albus seems to have inherited a little bit of everyone he is named after so I wouldn’t be surprised if he ended up being gay like Dumbledore. And Scorpius is everything is father wasn’t and therefore wouldn’t be surprised if he did end up being gay, unlike Draco.

Plus I think a Scorpius and Albus relationship would be pretty cute