My brother was so religious and after few years he turned upside down. He began to commit many sins, such as earning ill-gotten money, lying, cheating, bearing false testimony and giving precedence to his own interests over everything. Is it possible to call him to the true path? What can I do for him?

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.

Allah controls people's hearts, as the Prophet informed us. He further told us that Allah, changes people's hearts however He Wills.  [Muslim]

Therefore it is not impossible for Allah to guide your brother and enlighten his heart, but the matter needs wisdom and patience and the help of Allah. So, you should continue to admonish him.

We recommend that you try to get close to him and gain his affection. Perhaps this radical change resulted from a psychological problem, so help him to restore the power of his faith and do not belittle him. Do not expose his faults to people and give him hope for the best. Remind him of his former religiousness and let him meet some good and righteous friends and recommend that they take care of him, visit him regularly and allow him to participate in their activities. Lastly, do not give up supplicating Allah to guide him.

Allah Knows best.