I'm pretty sure you could use SimPE to set a sibling relationship for Pascal and Lola. Being so new to SimPE, I'm not sure how, but seems like I've heard of people doing it.

I have used InSim to make sims into siblings, though. I had to create a sim to be the parent, then make the others his children. InSim doesn't seem to have a way to make them siblings without a parent involved -- probably something to do with the way the family tree is coded. I did this with the Curious brothers in Mnemosyne.

If I remember right, you don't use InSim? How about SimPE?