I purchased 2- 2 month old siblings yesterday. New to glider babies. Do I need to be giving them a milk substitute? And I'm also freaking out a bit because I read that they can mate at 4.5-6 months old. Will siblings mate?? They seem to be bonded. I don't want to separate. What nutritional diet do I need for them? How should I deal with the potential of babies, I know neutering is an option. At what age can they be neutered?? Calling all local vets (think there is only one exotic vet in area). Any advice is welcome!

Congrats on your new gliders! The babies are old enough to eat grown up food. They are weaned from their mothers around 8 weeks and don't need a milk substitute.
As far as what to feed them, pick a staple diet. Common ones are OHPW (NOT HPW from Exotic Nutrition), BML and TPG. You can Google those or I can give you links or more info if you want. #128513;

Yes, siblings will mate. If you have a Male and a female they will mate, have Joey's and the Joey's will have problems because of inbreeding. You definitely want to get the Male neutered as soon as possible. Depending on the vet, I believe that males can be neutered at 9+ weeks. Some vets have weight restrictions.
If you have any other questions, don't hesitate to ask here, PM me or email me (my email is in my profile).

Thank you! But why can they not have HPW from exotic nutrition? And what do the synonyms stand for? I always fed my older glider (past away) glider food from Petco/PetSmart/tractor suppy or kibble (idk what to actually call it) from exotic nutrition. I guess I have tons to learn. I would love the links that you have.

It's been linked to illness in gliders. A friend of mine, who fed HPW, just recently had her glider have repeated seizures and it ended up being diet related.
The synonyms stand for:
OHPW - Original High Protien Wombaroo Diet
Link to the recipe: https://info.petsugargliders.com/staple-diets/ohpw/
Link to where to buy suplies: https://thepamperedglider.com/product/critter-love-original-triple-pack/
Link to the "salads" fed alongside: https://www.critterlove.com/salad-mixtures

BML - Bourbon's Modified Leadbeaters Diet
Link to recipe: https://bmldiet.com/bml-recipe.html

TPG - The Pet Glider Diet
Link to recipe: https://www.thepetglider.com/pages/tpg-diet#Recipe
Link to supplement that must be fed on top: https://www.thepetglider.com/collections/vitamins

Let me know if you have any other questions! :)