My boyfriend hasn't introduced me to his family?

i'm 20 and my boyfriend is 25. we have been together 4 months now. he has met all my immediate family (mom dad brother & sister) but for some reason i haven't met any of his family. he tells me that he's just not as close with his family as i am with mine. (i am very close with my family & he has only gone to see his family once since i've known him). i was just wondering if this is just an excuse or if this should be of concern and how to handle this. his family knows i exist, i'm friends with his mom and sister on facebook. he's also told me he loves me. should i be concerned?
My boyfriend hasn't introduced me to his family?
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