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, sallallaahu 'alayhi wa sallam, is His slave and Messenger.
A sister is among one’s Mahram women (i.e., someone whom a person is permanently forbidden from marrying), because it is permanently prohibited for her brother to marry her. Allah, The Exalted, Says, in the verse that mentions the women who are forbidden to a man for marriage, (what means): {Prohibited to you [for marriage] are your mothers, your daughters, your sisters …} [Quran 4:23] Therefore, it is permissible for her brother to shake hands with her as well as embrace and kiss her, provided that this is done without lust. Some scholars forbade kissing on the mouth, in particular, because it is often lustful. Safety from Fitnah (temptation) is a condition in handshaking, embracing, or kissing (between a brother and sister); if there is fear of Fitnah, then none of that is permissible.
We would like to point out that, in recent times, there has been many incidents of persons being tempted by their Mahram women and committing sexual harassment against them, and even committing incest with them. This is mostly caused by the degraded media content, watching movies, and using the Internet to access pornographic websites. A Muslim should not lose sight of this peril when interacting with his/her Mahaarim (plural Mahram).
Allah Knows best.