Don't agonize over it too much. Be generous. Are you paying him a salary as well?
I'm not making things up here, either. Every successful entrepreneur I know agrees with that sentiment, as does the prevailing philosophy of investors[1][2], thought leaders[3], and serial entrepreneurs[4].
I have never once seen anyone successful say to hoard your equity, especially if you're bootstrapped and cash-flow positive. Greed is a great way to kill morale.
1. http://hunterwalk.com/2014/11/26/one-founder-told-me-he-want...
2. http://blog.samaltman.com/employee-retention
3. https://news.ycombinator.com/item?id=8109
4. http://jamesaltucher.quora.com/The-Ultimate-Cheat-Sheet-For-...