Nothing good can come from this . U are at an age where u are learning more about ur body and be dating someone who stimulates your mind as well as your body . Your cousin is a horny 17 yr old that would put his penis in a knot in a wood if it were the only thing around . Its unhealthy and later in life if u have families they could get hurt if the relationship were to be rekindled . I know because my wife was you 26 yrs ago and theirs rekindled and lasted on and off for 11 yrs . I found letters and everything . Got messy so i speak from experience . Explain that it was what it was and can never be . Looks didn ' t matter to her either which was crazy cuz this guy looked puke he needed a bath when he just got out of one . Anyways just my opinion that nothing good can come from your relationship outside of momentary fun .