Co-founder pushed out

I'm being asked to leave a startup I've been with for almost 2 years, not due to performance but because the other two founders want more equity and think they can "take it from here". We each agreed to split 1/3 of the equity in 2015 but we didn't sign a founders agreement (only agreed by email).

Any advice how much % I should take and any other demands I should make? I don't see it working out with these guys. Thanks!!!