Hanameel was strictly the first-cousin of Jeremiah. In Hebrew all the terms of relationship are used in a more loose way than with us.
Related Commentaries of Jeremiah 32:7
Jeremiah 32:7
7 Behold, Hanameel the son of Shallum thine uncle shall come unto thee, saying, Buy thee my field that is in Anathoth: for the right of redemption is thine to buy it.