If my boyfriend can name me as beneficiary on his SGLI instead of his mother?

My boyfriend recently joined the army reserve and when it came to filling out the beneficiary he thought he had to put a relative as his beneficiary so he put his mom and not myself We have been together for years and his mom and dad are divorced and both well off. The only person whose life would be drastically altered (financially speaking) by his death...and I feel I should be the one to get it as there will still be house payments, car payments etc. Does anyone know about this family member rule? I think he just misunderstood and would be too shy to inquire further at the risk of feeling stupid.