If a man sucked the same milk with another Muslim girl from the same mother. Will his brother be able to marry her?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

There is no blame on one to marry his foster brother's sister as long as she is not his (foster brother) foster sister or half sister, since Allah, The Great and Almighty, has prohibited foster sisters.

Allah Says (what means): {… your foster milk suckling sisters.} [Quran 4:23]

Thus, there is no objection to marry sisters of foster brothers, as stated above if there is no other reason that forbids to marry her.

Allah knows best.