FWIW we adopted 'inseparable' sibling cats and they don't see much of each other as adults. Girl cat has the house as her territory and boy cat has the garden. He likes to ambush her quite hard if she ventured out
But they still sometimes curl up together if it's a cold night.
It's hard to say with cats sometimes. Their body language can be quite nuanced and swiping may not mean outright hostility, just setting boundaries.
It could also be the new scents that have disrupted their relationship. Cats signal friendship to one another by mixing scents, and avoid conflict by keeping their distance. As they've moved to a new 'territory' the conflict could be in part caused by smelling less of one another combined by still being on the same or overlapping 'territory'.
If you're worried about their aggression try feeding them in separate rooms and giving each its own litter tray. Being able to eat and poo separately could help de-escalate conflict.
Meanwhile take a hanky and wipe it gently around one cat's face area, following the fur/whisker direction, while feeding a small treat. Then repeat, with the same hanky, on the second cat. Then re-wipe the same hanky on the first cat. That will transfer scent from the cats' face scent glands between them, while associating the scent sharing with nice treats. If you repeat this every so often it can help 'mediate' and re-establish the relationship.
In this way you're giving them opportunities to have more space whilst at the same time mixing scents for them in a way that signals friendship.