Would the siblings be different if it was truthlesstruth
Oh boy, this is going to be a long answer... So! Let's just say that Sage of Truth met the twins MUCH later than Shadow Milk did!
In my au for TruthlessTruth, they learned to co-exist without too big of an issue.. Well, agreed to disagree at least. Sage technically still teaches at the Academy, but he agreed to not tell anyone about the existence of the Peak of Truth (For now...). So now we came to an agreement, our two "deities" only see each other every other decade, and Recluse wanted to keep his children safe by keeping them mostly close to the spire. Of course, every now and then they would be allowed to go to the nearby kingdoms town market and that is exactly where they started being interested in who their father could be seeing all the families. Well.. Blueberry IceCream was more interested. Vanilla Sundae didn't care too much-
Either way! Since Truthless didn't really want to talk about Sage much, on their 15th birthday, Berry asked to be able to meet the scholar, and how could Recluse possibly deny such a request? That is why he gave them every information they would need to find him.. (Even if he was worried SICK. Then again, they are old enough to protect themselfs so it should be fine..)
For Sage it was just another day strolling around the the Academy when suddenly two teens just approached him, started calling him dad and asking way too many questions at once! It was.. Let's be honest, a strange day at the academy. He was of course happy to answer all the questions, but there will be a very long and uncomfortable conversation with a certain Hermit...
And now for the question you're probably more interested about.. Berry didn't exactly change much. She's still a troublemaker who drags her brother around causing trouble. One big change with her is that she planned a couple escapes from the Spire which she never would even think of doing from the Vanilla Kingdom in the main au.
Sunday changed MUCH more. Not only did his species change since in my headcanon PV changed from a sheep hybrid to a halovian during his awakening which didn't happen with Recluse, but he's also much more reserved with no interest for the outside world, taking a lot from Recluse (as a younger child he would follow him around everywhere) So with this little guy, not only did his personality slightly changed, but also his design. But don't worry, he still loves a little dress up and a debate. Maye that is just something he got from his dads genes no matter how he was raised...