Wiktionary
paternal aunt
n. the sister or sister-in-law of one's father
Usage examples of "paternal aunt".
Three years later, her paternal aunt died unexpectedly, leaving Jilly a small fortune, and telling her in a letter that she had felt it only right to leave her the money because she had been so wronged by her father.
I amended that: this baby would have a relationship, for its proxy mother was its paternal aunt.
Subject's last known relative, a paternal aunt, died eighteen months ago.