Former DUP Foyle MLA William Hay, who now sits in the House of Lords as Lord Hay of Ballyore, has not joined his twin sister Annette and his sister Christine in switching party allegiance to the TUV.
But it is reported that both sisters have now appeared in a campaign video endorsing TUV candidate Elizabeth Neely, alongside the TUV leader Jim Allister.
In the video, Mr Allister said: “I’m in Foyle with our candidate Elizabeth Neely, and I’m particularly delighted to be joined in support by two ladies who are the sisters of Lord Hay, Willie Hay of the DUP, which is an indication of the growing support for the TUV campaign.
“There’s a realisation that this is a big opportunity, maybe a last opportunity, for unionism to stand firm, that unionism has nothing left to give, that we must dig our heels in and send a very clear message that we can neither live with this Protocol nor the ongoing failures of Stormont. “
He added: “It’s time for unionists to unite against all those things by voting for the unionist party they can now trust, the TUV. So on that basis we are moving forward across Northern Ireland and not least here in the constituency of Foyle, and drawing together people who recognise in TUV the authentic voice of unionism that they want to see prosper.”
Ms Neely, speaking to the News Letter, said she had also switched allegiance to the TUV recently over the Northern Ireland Protocol.
“The Irish sea border was the last straw for me,” she said. “I have had great support with Lord Hay’s sisters who are fully behind me and supporting me.”
This comes after the DUP veteran Jim Wells switched allegiance to the TUV to endorse the party’s candidate in South Down, Harold McKee.
That move was also followed by the resignation of several DUP officers in South Down, who moved to back the TUV’s Mr McKee.
Voters go to the polls this Thursday, May 5.
In the Foyle constituency, five candidates will be picked for the Assembly.
At the last Assembly elections, the SDLP and Sinn Fein both got two seats and the DUP won one seat.