The parents of the former Ulster Unionist MP, Mr Jeffrey Donaldson, have been guests of the President, Mrs McAleese, at Áras an Úachtaráin.
DUP members including the mayor of Ballymoney, Cllr Frank Campbell, have also attended formal dinners hosted by the President as part of her aim of "building bridges".
Mr Donaldson, who severed his connections last week with the Ulster Unionist Party, said he had "always maintained that it is important for unionists to put their case south of the Border" and to enhance mutual respect and understanding between Northern Ireland and the Republic.
The Lagan Valley MP said yesterday that "many citizens of the Republic visit Buckingham Palace" and he saw no difficulty with visiting Áras an Úachtaráin. The only area where unionists might have a "quarrel" would be a concern that President McAleese "might overstep the mark" in terms of some of her visits to Northern Ireland, he said.
Cllr Campbell described President McAleese as "very progressive".
He was a guest last year and also visited the Áras three years ago. DUP members were regular visitors to the South, he added, and such contacts were going to be "the way forward".
His visit was discussed within the party, and there was no hostility when he explained why he went. "I'm not sure if they see me as rebellious," he said, but added that he would like to see progress.
Mr Donaldson's father, Mr Jim Donaldson, was a South Down candidate in the Northern assembly elections. The couple is believed to have dined at the Áras earlier this year, but a spokeswoman for the President declined to comment on their visit.
She pointed out that since the beginning of her term in office the President had sought to extend the hand of friendship. "She is not doing it to try and influence people and change their minds," she added.
Áras an Úachtaráin was "a repository of British history as much as Irish history" from its early days as the viceregal lodge through its various guises over the past 250 years.
The President and Mr Martin McAleese host parties and dinners every second or third week.
