A person who is "beloved" is very loved such as your husband/wife or parents.Generally it is a person who we have loved for a long time or very deeply, so boyfriend or girlfriend do not usually earn the title "beloved " although some might refer them to as their beloved but not often correctly

Hi Natasha the word " beloved" can be use on a person very dear to you, and you can definitely use this word on your boyfriend or husband. Hope this helps.