Whether he dies before OTL's Charles II is conceived, or during the Civil War as OTL (not overly plausible given the butterflies), or some other combination is up to you. But it must after the OTL death of James I and VI.
Anyway, who succeeds him? Elizabeth and her husband? (kinda *William and Mary half a century early). Or is that politically infeasible? If that solution isn't possible, who has the next best claim?