Verses with the word sister's in the New Testament (2 verses):

Acts 23:16
And when Paul's sister's son heard of their lying in wait, he went and entered into the castle, and told Paul.

Colossians 4:10
Aristarchus my fellowprisoner saluteth you, and Marcus, sister's son to Barnabas, (touching whom ye received commandments: if he come unto you, receive him;)