Sir Andy Murray and wife Kim welcome baby boy

Sir Andy Murray and wife Kim Sears are celebrating the arrival of their third child, according to the tennis ace's grandfather.

Roy Erskine, 88, said that the couple's new arrival is a "wee boy" who is understood to have been born in London last week.

"He was born during the week, I don't know his name yet," Erskine told The Scottish Sun, adding that his wife has been to visit the newborn.

He added that he had seen "photographs on [his] wife's phone" of the baby.

Loved up: The couple are already parents to two young girls (PA Archive/PA Images)

"They're both doing fine, I'm just glad that it's all over," he continued.

The Murrays are already parents to Sophia, three, and Edie, two.

Standard Online has contacted representatives for the couple for further comment.

Murray confirmed last month that he would take a short break from tennis as the family prepared for the new arrival.

"I'll definitely be taking some time off as we'll be pretty busy with three children under the age of four," he told The Times.

"I'll try to be around as much as possible in the next year, but I know my tennis career won't go on forever so there will need to be a balance between me maximising the next few years and spending quality time with my family.

"I'm lucky in that I can train close to home, so that lets me do things like the school run wherever I can."

He recently returned to singles competition following a hip resurfacing operation and won the European Open in Antwerp last month.

Murray and Sears married in 2015.