What is wrong with "Твой братья едят суп"?
"Твой" is for one masculine object, "Твои" is for multiple objects. Since there are multiple objects in this sentence, you should use the latter.
Whats wrong with "тебя братья ешь суп"?
"ешь" is single person as in "you eat", "братья" calls for plural, thus "they eat" = "едят"
«тебя» is accusative, not genitive.
Тебя is the genitive and accusative (male) form of ты, but here you need the possessive pronoun твои/ваши which is nominative plural of твой/ваш
Why cant you use "кушают"?
In English you drink soup not eat it.
Man, the Russian alphabet is so weird!!
It is, but it's all i got. Dennis, I agree