Demographic attributes in personas are important for building empathy for the user, and in helping your teammates remember them (Nielsen Norman Group). However, they're typically not the best differentiator, as you could have two 28 y.o. mothers who belong to completely different personas. That's because they have different mental models, pain points, and motivations.
Millennial Mom Megan and Grandpa Gary might both use Venmo to send money. That's the goal, and it's shared. They might also both be frustrated with a shared pain point - maybe they don't like waiting 1-3 days for bank transactions, or having to pay for instant transfer.
However, when you look at the motivations and why they're sending money, you'll find differences. Megan does a good bit of her day-to-day spending with Venmo, because it's what her friends and vendors prepare to use. Gary, on the other hand, hates using Venmo in general - he'd still rather just use the one credit card he uses everywhere - and only uses Venmo once in a long while to send money to his grandkids for their birthdays, because that's what they prefer.
When you dig into the why, you get interesting variants. In fact, it's a good practice to name your personas after these attributes - Every Payment Elizabeth, Stingy Steve.
Another important way to distinguish personas is by their relationship to your business. Megan might be far more profitable of a customer than Gary. You might create Gary as an "anti-persona", or the kind of customer you don't want because he'll cost your business more than you earn from him. You could look at income, average lifecycle spend, future opportunities, and so on to figure this out.
