Is it permissible for a full brother to marry his brother's daughter by suckling?

If your male cousin was suckled by your mother five times or more within the first two years (of his life), then it is not permissible for your paternal half-brother to marry his daughter, because she is his sister through rada'ah (suckling). This is based on the Prophet's (peace and blessings be upon him) saying: "What is prohibited by lineage is also prohibited by suckling."