Should my fiance and I ask our respective parents for an increase in our allowance?

Honey if you're going to be a grown up with a family you shouldn't be getting an allowance at all never mind an increase. If you need some help with buying baby furniture or whatever and you're parents are willing and able to help then be thankful but you can't expect to get an allowance when you're a grown married woman. You're going to be the adults in your own family now so you're going to have to learn how to get by on your own money.