Does the sin of severing kinship ties fall upon me or upon my brother, who wronged me and cut me off, even though I have forgiven him and he continues to shun me?

The sin of severance falls upon the unjust severer. If you connect with your brother—even if by greeting him and asking about him via phone—and he then turns away, there is no blame upon you. Do not let his turning away lead you to sever ties with him. Rather, continue to connect with him and be kind to him, for the one who maintains ties is not he who reciprocates, but rather he who maintains kinship even when it is severed. The Prophet, peace and blessings be upon him, clarified that whoever maintains ties with his relatives who cut him off, and is kind to them despite their ill-treatment, it is as if he is feeding them hot ashes, and he will always have a supporter from Allah against them.