I have seen this a couple of times. The only reason you wouldn't do an equal split is: (a) if they have substantially more experience or have a more valuable s

I have seen this a couple of times. The only reason you wouldn't do an equal split is: (a) if they have substantially more experience or have a more valuable skillset. For example, prior to this role they could command a salary that was twice what you could make in the market. (b) they have substantial traction already. Revenue, customers, funding, team momentum, etc. Neither of these seem to be true. "I came up with the idea" is not enough to warrant a difference in equity. Honestly, the fact that they didn't offer you co-founder and equal equity is the first flag. Working with his brother is the second flag.