You could use estéis too. In this case we used seas (ser) because the speaker is referring to an inherent quality of that person, as in he is genuinely a jealous guy, part of his personality. If you use estar, then you are referring to this person "getting" jealous in a precise moment for a specific reason, not necessarily meaning that this is the sort of person he is. It is a temporary thing.
I hope it clarified it.
Yes, thank you. This is a wonderful explanation
Sign in to submit your answer
Don't have an account yet? Join today
Test your Spanish to the CEFR standard