Gareth Southgate had hoped he would choose England with McTominay in demand after making his breakthrough at Old Trafford.
But grandfather Frank told the National: "Alex McLeish handled the situation quite well," he told the National . "
"It's been rumbling on now for two or three months now in the papers. But he didn't go shouting and bawling. He just said that he would speak to Scott and he did. He conducted himself quite well.
"But Sir Alex Ferguson was keen for Scott to play for Scotland as well. He was up front about it. I know that for a fact. I can say that without fear of getting contradicted. That has been kept under wraps. He and Jose Mourinho were both quite keen on it over the last month or two.
"Sir Alex Ferguson has been very good with Scott over the years. He gave him his first contract with Manchester United when he was 16 before he retired and then made sure it was extended when he was 18. He seems to get on well with him. I have seen them talking."