Need suggestions on equity split between founders for a SaaS product

Hi,

I have a question about founder equity-split.

3 months back, me and one of my acquaintance started working on a SaaS idea. It was mostly an already existing idea (a knowledge-base system) but my cofounder convinced me that it's still worth building because he knows there are potential customers and it might be a good way to get started with SaaS in general.

So I took care of all-things-tech and put up an MVP in roughly two months. We ran campaigns (my cofounder knows multiple potential customers and is well resourced in that sense) but haven't had a paying customer yet (might be due to COVID, but of course the product might be the cause as well).

Now fast forward one month, we are trying to adapt our solution for Shopify ecosystem, and my cofounder introduced me to another guy who's working with Shopify app companies for the last 3-4 years. His proposal is to onboard him as a cofounder, which I'm also happy to, but now the big question for me is,

"How should the equity be divided among three or us?"

I proposed it to be split half between me and my first co-founder, and slightly less to the newly onboarded guy. But my co-founder doesn't seem to agree with equal split, he thinks I should have a lesser equity share and said that that's usually the case with other SaaS companies too because SaaS is marketing intensive.

I was wondering if someone is aware of what the right split could be (or what's the usual trend) and can share that knowledge here.

PS: I know, I should've talked all this out in the very beginning, that's a mistake on my part.