Kiernan, 24, is on the books at recently-relegated Wigan, but spent the end of last season on loan with Birmingham City, playing 12 games and scoring once for the Blues.
Now back with Wigan, Kiernan could be on the move rather than play in League One, with Rangers allegedly having a bid accepted for the centre back.
New Rangers boss Mark Warburton not only worked with Kiernan during his time as a coach at Watford, but even helped signed the Irishman on loan as Brentford's sporting director.
A third spell together is now on the cards, with STV reporting that Rangers have agreed an undisclosed fee with the Latics for Kiernan's signature.
Having allowed Bilel Mohsni and Lee McCulloch to leave Ibrox on free transfers this summer, Rangers need help in defence and Kiernan - who previously had a loan spell in Scotland with Kilmarnock - is seen as the man to help ease those defensive woes.
A former Republic of Ireland Under-21 international, Kiernan has spent most of his career out on loan so will now be looking to settle down and play regular first-team football - and a reunion with Warburton could give him the best chance of doing that.