Okay let me spell it out then.
MA:
• Age of Consent is 16. There is no differential so 16 - 17 year olds can only have sexual relationships with people their own age.
Alabama:
• Age of consent is 16. But has a minimum age of victim as 12, where the victim can never consent. Differential is 2 years if victim is above the minimum age. And minimum age of defendant being prosecuted is 16 years old. So if a 16 year old had sex with a 15 year old even though the 15 year old is not considered the Age of Consent it’s not considered statutory rape. So a 17 year old and 19 year old can have a relationship based on what the law says about a 2 year differential.
18 is Age of Majority and should not be confused with Age of Consent.