The popular ITV series that traces people's missing or unknown relatives returns on Monday with its Born Without Trace spin-off show, where people abandoned at birth search for information on their background.
It is a subject that comes with emotional discoveries for those taking part and the news is not always what they want to hear — something McCall, who co-presents with Nicky Campbell, finds difficult to handle.
She said: "To be honest, something I have found very hard but I have tried to learn over time is that I have to let people feel all the feelings that they feel and not try and make them happy or make it feel better.
"For example with Niki, whose story is in the third episode, she had to deal with something big and I know it has really been hard. To find out that her parents had other children together but left her. And when I spoke to Niki, I couldn’t take that pain away.
"So if she was angry, it was alright for her to be angry. That was a justified response and I mustn’t try and take that away."
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She continued: "The temptation to try and make it better and say, ‘But look isn’t this brilliant you’ve got four siblings?’, is so huge, but it’s not what I should be doing."
In the new series, some of the people searching for their families discover that they were given up by married parents, who in some cases kept older and younger full siblings living with them.
McCall added that whatever they found out about people's backgrounds, it could be enormous news for them if they had no idea where they had come from.
She said: "When I’m go to see them to give them information, it’s much, much more slowly (than in Long Lost Family's main series). Because they’ve never heard anything.
"I may something like, ‘I have news’. And then I won’t speak for three minutes. Because even the possibility of news is so big that it takes ages for it to filter through and process.
"And then I just wait for them to ask me a question."
Long Lost Family: Born Without Trace airs on Monday, Tuesday and Wednesday at 9pm on ITV.
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