Could use some guest list help please 
Fiance and I can invite 150 people to our wedding. I come from a large, close-knit family (my parents each have 5 siblings, and I have more than twenty first cousins.) Fiance comes from a much smaller family (one aunt and uncle, three first cousins.) What's the protocol with dividing the guest list between our families? If we told both sets of parents they had to invite the same number of guests to keep it fair (say, 50 each) then my parents would only be able to invite their siblings and their children, while my fiance's family would be able to include extended family members and friends too.
My parents are paying for the wedding. My fiance's parents are not contributing, nor do I expect them to. They are not in a financial position to help, and I am totally fine with that. I just feel fortunate that my parents are able to contribute so much.
What is the proper thing to do? Is it OK to allot my parents more of the guest list than my fiance's parents? Or is that poor etiquette? Any advice would be much appreciated!