@DrRansom it is "atsilí" . Word for word, it means "younger-brother by-him he-exists". Alternately, you could consider the subject to be "there", like in "younger-brother by-him there-is".
Thank you! Great explanation. So how do you know "bee" refers to "him" (singular masculine 3rd person) rather than another pronoun?
This you have to know... Prefix b- in prepositions, verbs, noun, is the 3rd person prefix (no distinction of gender or number). So: Shimá (my mother) , bimá (his mother), shee (by me), bee (by him), etc..
Btw this sentence should be: bitsilí hólǫ́ (his-brother there-is).