Ask HN/YC: Early stage startup, equity for a non executive co-founder

I am working on an early state startup with three others.

Three out of the four in the team have worked together in our previous startup, where I was an early employee. We have worked with each other for about 6 years now.

Now, between the other three, one is going to be the CEO, the other VP of Engineering and the last VP of Sales and Biz Dev. I will be the 'architect' for the startup.

We have been working on this for a few months now and we are now talking to VCs to raise funds. My question to HN / YC is 'What is a fair % of equity for me at this stage?'. Given the past history and trust between us, if there is an issue with equity, what is the best way to deal with it?

Thanks.