Simeon and Levi are brothers
This does not just mean they are brothers by birth. Jacob is emphasizing that they worked together to kill the people of Shechem.
Weapons of violence are their swords
"They use their swords to hurt and to kill people"
O my soul ... my heart
Jacob uses the words "soul" and "heart" to refer to himself and is saying that other people,and perhaps God also, honor him so much that he does not wish to join with those who make plans to do evil. (See: rc://en/ta/man/translate/figs-synecdoche)
do not come into their council; do not join in their meetings
These two phrases mean basically the same thing. Jacob combines them to emphasize that he does not want to participate in their wicked plans. AT: "I certainly will not join with them to make any plans" (See: rc://en/ta/man/translate/figs-parallelism)
they hamstrung oxen
This refers to Simeon and Levi crippling oxen just for fun.
This refers to cutting the sinews of an animal's leg so that it cannot walk.