I'm looking for a mod that will allow me to connect a toddler/child/teen etc. to an elder instead of an adult. I know I could age the adult up later and change the relationships with the Sim blender but is there a way around this?

There isn't a way to do this in CAS, unfortunately. The types of families that can be created in CAS can't be changed, as far as I know. If you want your family tree to look correct, the best way would probably be to age sims up or down to the ages you want, like you described, or to edit sims' family trees in SimPE. I believe mods like the insimenator or sim blender can also change family ties in game.

Honestly, if I were you, I would just adjust the ages of sims and then use the Memory Manipulator to remove memories I didn't want/rearrange them. But the Sim Blender can be found in twojeffs' archive if you don't already have it; look under mods, and then your highest EP.

I'll look into that. Thank you!